She was supposed to be at a birthday party. Instead, she was loading a gun in her car, hands trembling, heart racing, scrolling through Instagram photos of the woman who’d stolen her entire world. Instagram photos flashed. Happy couple date nights. Loving captions. Y’all, this ain’t just another love triangle gone wrong.
This is the story of how jealousy, obsession, and rage turned a 26-year-old dental assistant into a coldblooded killer. On the night of October 14th, 2023, in the quiet suburbs of Riverside, California, a woman named Sienna Vale made a decision that would destroy three families forever. She didn’t just threaten her ex-boyfriend’s new girlfriend.
She didn’t just show up to scare her. She hunted her down like prey and pulled the trigger five times. But here’s the thing that makes this case absolutely insane. Sienna had been planning this for weeks. She’d been stalking her victim on social media, driving past her house, even befriending people close to her just to get information.
This wasn’t a crime of passion. This was premeditated murder wrapped up in the ugliest bow of jealousy you’ve ever seen. Now, you might be wondering what could make someone so consumed with rage that they’d throw away their entire life. What kind of relationship drama leads to actual literal murder? Stick around because this story has more twists than a pretzel factory.
And trust me, you ain’t ready for where this goes. This is Women Justice Files, where we dive deep into the cases that shock us, haunt us, and make us question what we think we know about human nature. So, here’s the thing about Sienna Vale. If you’d met her 3 years before this murder, you probably would have thought she was just another girl trying to make it work.
Pretty ambitious, a little highmaintenance maybe, but nothing that screamed future killer. Sienna Marie Vale was born on June 3rd, 1997 in Orange County, California to middleclass parents who by all accounts gave her a decent childhood. Her mom, Linda, worked as a nurse at a local hospital, often pulling long shifts, but always making sure there was a hot meal on the table when she got home.
Her dad, Robert, was a construction foreman, a man who believed in hard work and discipline, but doted on his daughter. She had one younger brother, Tyler, who she was reportedly close to growing up. The Veale family lived in a nice two-story house with a manicured lawn, the kind of place where neighbors waved to each other and kids played safely in the culdesac until the street lights came on.
Looking at home videos from that time, you see a seemingly idyllic picture. There’s footage of Sienna at age seven, missing her two front teeth, proudly holding up a soccer trophy. There are clips of Christmas mornings, birthdays with pink frosted cakes, and family trips to Disneyland. But if you dig a little deeper, cracks begin to show.
Even back then, teachers from her elementary school recall a child who struggled immensely with sharing attention. One teacher, Mrs. Gable, remembered an incident in second grade where Sienna threw a tantrum because another girl was chosen as the line leader. A role Sienna felt entitled to. It wasn’t just a normal childhood fit. Mrs.
Gable described it as intense, focused rage where Sienna refused to speak to the other girl for weeks. It was an early sign of a personality that demanded to be the center of her universe. A trait that would only metastasize as she grew older. In high school, Sienna was that girl. You know the type. Popular enough to matter, pretty enough to date whoever she wanted, but not quite secure enough to be genuinely confident.
She was a cheerleader at Canyon Hills High School, made decent grades, and had a tight circle of girlfriends who she’d known since middle school. She wore the right clothes, listened to the right music, and seemed to fit perfectly into the social hierarchy of suburban teenage life. Even back then, people who knew Sienna said there was something intense about her.
She wasn’t violent or anything, but she was possessive, clingy, the type who’d lose her absolute mind if her boyfriend even looked at another girl. Her friends learned quickly not to mention other girls around her when she was dating someone. It was an unwritten rule. Sienna’s boyfriend was Sienna’s property, and any threat to that ownership, real or imagined, was met with icy silence or explosive outbursts.
Her ex-boyfriend from junior year, a guy named Brandon, later told investigators about the suffocating nature of their relationship. He recalled that Sienna once showed up at his house at 200 a.m. because she saw him comment a fire emoji on another girl’s Instagram post. A fire emoji. That’s all it took. She didn’t hit him or anything, but she sat in her car outside his house for 3 hours calling him over and over, sending hundreds of texts, spiraling because she’d convinced herself he was cheating.
He wasn’t. He’d literally just commented on a classmate’s post about homecoming. Brandon described looking out his window and seeing her car idling there in the darkness, the glow of her phone screen illuminating her face as she typed message after message. He felt trapped, scared even then, though he couldn’t articulate why.
Was that a red flag? Absolutely. Did anyone think it would lead to murder one day? Hell no. Most people just wrote it off as teenage drama. The kind of intensity that fades with maturity. But for Sienna, maturity didn’t bring perspective. It just gave her more sophisticated tools to monitor and control.
After high school, Sienna enrolled at Riverside Community College where she studied to become a dental assistant. It was a practical choice, one her parents supported. She graduated with her certificate in 2018, landed a job at a family dentistry practice in Corona, and seemed to be getting her life together.
Her co-workers described her as friendly, chatty, someone who’d always volunteer to grab lunch for everyone. She was good with patients, especially kids. She’d make them laugh during cleanings, give them stickers, the whole deal. Dr. Aris, the lead dentist, said Sienna was punctual and professional. She remembered patients names, asked about their weekends, and kept the office running smoothly.
But there was another side to Sienna that only came out in her personal life. A shadow self that she kept carefully hidden behind her scrubs and bright smile. Sienna had this pattern. And looking back, it’s crystal clear. She’d get into relationships fast. First date on Monday, exclusive by Friday, talking about moving in together by week three.
She craved the high of new love, that oxytocin rush where two people become one. She’d love bomb whoever she was dating, showering them with gifts, constant affection, texts every five minutes. At first, guys ate it up. Who wouldn’t? Beautiful girl, completely devoted, making you feel like you’re the center of her universe.
It felt like winning the lottery. But then the possessiveness would kick in. The texts would turn from sweet to demanding. The gifts would come with strings attached. The devotion would start to feel like surveillance. She’d need to know where her boyfriend was at all times. If a location pin wasn’t shared, she’d accuse him of hiding something.
She’d check his phone while he was sleeping, scrolling through years of messages, looking for evidence of betrayal that didn’t exist. She’d create fake Instagram accounts to see if he’d respond to other girls sliding into his DMS, testing his loyalty in twisted games he didn’t even know he was playing. She’d start fights over the smallest things.
Him going out with his boys liking a celebrity’s photo, talking about a female coworker. Her ex-boyfriend from 2019, Marcus told police Sienna, once threw his phone into a pool because a girl he went to high school with sent him a happy birthday message. A birthday message from someone he hadn’t seen in 4 years. Marcus described the scene vividly.
The splash of the phone hitting the water. The look of pure unadulterated rage on Sienna’s face. And then the sudden switch to tears as she begged him not to leave her, claiming she only did it because she loved him so much. Marcus broke up with her after 6 months. He said the jealousy was too much. He couldn’t even go to the gym without her accusing him of trying to meet women.
He felt like he was living in a prison where the warden claimed to love him. But it was her next relationship that would set everything in motion. Enter Matteo Cruz, 28 years old, personal trainer, tattoos, killer smile, the kind of guy who looked good in literally everything and knew it. Matteo was charismatic, the life of the party, someone who made friends wherever he went.
He had a tight-knit family and a large circle of friends who adored him. Sienna met Matteo in January 2022 at a CrossFit gym in Riverside. She just joined, trying to get in shape for her friend’s summer wedding. He was one of the trainers there, known for pushing his clients hard, but always with encouragement. According to everyone who witnessed it, the chemistry was instant.
It was electric. You could feel the pull between them from across the room. They became that couple, posting gym selfies together, doing partner workouts, commenting heart emojis on every single post. Their social media was a curated highlight reel of romance. Beach dates in Lagona, hiking trips to Joshua Tree, cozy nights in with wine and movies.
Within two months, Sienna had basically moved into Matteo’s apartment. Her toothbrush was in the holder. Her clothes filled half the closet. Her presence was everywhere. For the first time in her life, Sienna seemed genuinely happy. She posted constantly about Matteo, my king, my everything. Can’t believe I got so lucky.
She’d bring him lunch at work, surprise him with little gifts like new sneakers or protein supplements, plan elaborate date nights. Matteo’s friends said he was pretty into it at first. Sienna was hot. She was fun when she wasn’t being crazy jealous, and she treated him really well. He told his buddies that he’d never met anyone who cared about him so much.
However, the honeymoon phase can only hide the cracks for so long. About 4 months in, Matteo started noticing the same patterns his predecessors had seen. It started subtly. A comment here about a female client being too friendly. A question there about why he took so long to reply to a text, but it escalated quickly.
Sienna needed constant reassurance. She’d flip out if he didn’t text back within 10 minutes, sending a barrage of question marks followed by accusations. She’d show up at the gym unannounced to bring him a protein shake, but really just to make sure he wasn’t training any attractive female clients. She would stand by the reception desk watching him work, her eyes tracking his every interaction.
It made Matteo uncomfortable. It made his clients uncomfortable. The text messages between them started getting darker. She’d accuse him of cheating with zero evidence. She’d threaten to hurt herself if he tried to leave. She’d say things like, “You’re all I have and I can’t live without you.
” It wasn’t romantic anymore. It was heavy. It was a burden. Matteo wasn’t perfect either. We have to be honest about the dynamics here. According to court documents and interviews with friends, he could be kind of a player. He enjoyed female attention. He’d flirt with other women at the gym, sometimes crossing the line from professional friendliness to playful banter.
He’d go out to bars with his boys and not tell Sienna until she’d already blown up his phone, trying to avoid the inevitable fight, but only making it worse. But let’s be absolutely clear. Being a kind of shitty boyfriend, being avoidant, or being flirtatious doesn’t mean you deserve to have your life destroyed. It doesn’t justify stalking, and it certainly doesn’t justify murder.
Relationships fail every day for these exact reasons, and people move on. But Sienna couldn’t move on. In August 2022, after 8 months together, the tension reached a breaking point. Matteo broke up with Sienna. He sat her down and told her he needed space, that the relationship was too intense, that he couldn’t deal with the jealousy anymore. He told her he felt suffocated.
Sienna absolutely lost it. It wasn’t a sad breakup. It was a catastrophic implosion. She screamed, she cried, she begged. She refused to leave his apartment for hours until he threatened to call her brother to come get her. According to her roommate, Kayla, Sienna spent three days in bed after the breakup, barely eating, crying constantly, checking Matteo’s Instagram every 5 minutes to see if he’d posted anything. The blinds were drawn.
The room smelled of stale air and despair. Kayla tried to comfort her, bringing her food she wouldn’t eat, but Sienna was inconsolable. But then, abruptly, something shifted. It was like a switch flipped. Sienna started posting again. Gym selfies with captions like new chapter and glow up season. She went out with her girlfriends posting stories of cocktails and dancing.
She started talking about focusing on herself, about how she didn’t need a man to be happy. To the outside world, it looked like resilience. Matteo’s friends told him she seemed like she was moving on. He felt relieved. He thought the worst was over. Maybe she’d finally accepted it. He could breathe again. But Sienna wasn’t moving on. Not even close.
She was spiraling in ways nobody could see. This new chapter was a facade, a carefully constructed mask to hide the obsession that was rotting her from the inside out. While she was posting smiling selfies, she was simultaneously logging into Matteo’s accounts, guessing his passwords, tracking his location. And what she didn’t know yet was that Matteo had already met someone new, someone who would become the unsuspecting target of all that suppressed rage.
Her name was Elina Mercer, 25 years old, elementary school teacher, beautiful smile, kind heart, everything Sienna was convinced she’d never be. Elena was the kind of person who radiated warmth. She taught third grade at Riverside Elementary where she was beloved by her students and colleagues alike. She had a patience that was endless, a gentle spirit that drew people to her.
She volunteered on weekends, loved hiking, and was close with her family. When Sienna found out about Elina, that’s when the obsession truly began to curdle into something dangerous. Before we get into how this obsession escalated into murder. If you’re enjoying this deep dive into the psychology of this case, please take a second to hit that subscribe button and turn on notifications.
We post new cases every week covering everything from forensic files to unsolved mysteries, and these algorithms ain’t going to do us any favors unless you show some love. It takes 2 seconds and helps us out so much. It was September 2022, exactly one month after Matteo broke up with Sienna, when she first discovered he was seeing someone new.
She didn’t find out through mutual friends or by running into them somewhere. Sienna found out because she’d been stalking Matteo’s social media like it was her full-time job. She spent hours every night analyzing his likes, his follows, his comments. It was digital forensic work fueled by madness. Matteo posted a photo at a restaurant downtown. Just him.
Solo pick caption about trying new places. Innocent enough. But Sienna noticed something in the background. A reflection in the window. A woman with long dark hair sitting across from him. You could barely see her, just a shadow, a silhouette against the glass. But Sienna zoomed in. She adjusted the brightness. She took a screenshot.
She became obsessed with figuring out who this shadow woman was. She went full detective mode. She looked through the comments on Matteo’s posts, found a guy who tagged the restaurant location, went to that guy’s profile, found his girlfriend, went through her followers until she found someone who’ posted from the same restaurant that night.
It was a tedious, winding path through the digital web. But Sienna was relentless. And that’s how she found Alina Mercer. She found a tagged photo of Elina at the same restaurant wearing a dress that matched the reflection. The puzzle piece fit. Elena’s Instagram was public. Big mistake in today’s world, but Alina had nothing to hide.
She was just a normal girl living her life. Sienna scrolled through every single post, every photo, every story highlight. She went back years. She learned where Elina worked. Riverside Elementary School. She learned where she liked to get coffee, a Starbucks on Magnolia Avenue. She learned what kind of car she drove, a white Honda Civic.
She learned the names of her friends, her dog, her favorite vacation spots. Sienna made a whole dossier on Elina like she was preparing for a mission. She consumed Elena’s digital life, trying to find flaws, trying to find reasons why she wasn’t good enough for Matteo, or conversely, why she was a threat. Sienna’s friend Jordan later testified that Sienna would send screenshots of Elena’s posts with nasty, degrading messages.
Can you believe this is who he chose? Sienna would text. She’s not even that pretty. Look at her nose. Look at her hair. She’s basic. Jordan tried to be supportive at first, telling Sienna she was prettier. That Matteo downgraded the usual things friends say to make you feel better after a breakup. But Sienna wouldn’t let it go.
The texts became more frequent and more vitriolic. But it wasn’t just online stalking. Sienna took it way further into the real world. According to cell phone records later obtained by police, Sienna drove past Elena’s apartment building at least 17 times in September alone. 17 times. Sometimes she went in the morning before work. Sometimes late at night.
She’d park down the street and just watch, waiting to see if Matteo’s car would show up. And when it did, the pain would see her through her. Sienna would take photos of his car in Elena’s driveway, send them to Matteo with messages like, “Hope you’re happy, and she’ll never love you like I did.” It was psychological warfare.
She wanted him to know she was watching. She wanted him to feel her presence. Matteo blocked her number. He blocked her on Instagram. He blocked her on Facebook, so she started texting from different numbers, apps like Text Now and Google Voice that let you create temporary numbers. She’d send me
ssages at 2:00 a.m., 4:00 a.m., sometimes 50 texts in one night. They ranged from pleading, “Please just talk to me,” to abusive, “You used me,” to ominous, “you’ll regret this.” It was a barrage of harassment that left Matteo feeling constantly on edge. He changed his locks. He started parking his car around the block.
He told his friends he felt like he was being hunted. You might be thinking, why didn’t Matteo just go to the police and get a restraining order? He actually tried in late September. He went to the Riverside Police Department, showed them the texts, explained the situation. But the law is tricky with this stuff. Unless there’s a direct credible threat of violence, like I am going to kill you, restraining orders can be hard to get, especially just based on annoying texts and drivebys that happen on public streets. Sienna never explicitly
threatened to physically harm him in those texts. She was unstable, sure, but legally speaking, she hadn’t crossed the line into criminal threat. The officer took a report, told Matteo to document everything, and sent him on his way. It’s a tragedy we see too often. The system reacting only after the violence happens, not preventing it.
October rolled around and Matteo and Elina had been dating for about 2 months. They were getting serious. Despite the drama with Sienna, their relationship was flourishing. Elina was understanding about the crazy ex situation, though she admitted it scared her a little. Matteo made her feel safe.
He even introduced Elina to his family at a Sunday barbecue. It was a big step. His parents loved her immediately. And somehow Sienna knew about it. She always knew. Matteo’s sister, Maria, posted photos from the barbecue on Facebook. Her profile was public, another oversight. In one of the photos, you could clearly see Matteo and Elina together, his arm around her, both smiling, holding red plastic cups. They looked happy.
They looked like a family. Sienna saw that photo on October 2nd at 11:47 p.m. We know this because she screenshotted it, and that screenshot was later recovered from her phone by forensic analysts. That photo broke her. It was the visual confirmation that she had been replaced, not just as a girlfriend, but as a part of his family, his future.
According to Kayla, Sienna became a different person after seeing that photo. She stopped going to work regularly, called in sick three times that week, jeopardizing the job she had held for years. She barely ate. She stopped going to the gym. She’d stay up all night looking at Elena’s social media, Matteo’s social media, going through old photos of her and Matteo together, comparing the timestamps, torturing herself with memories.
Kayla testified that the light went out of Sienna’s eyes. She started saying scary stuff like, “She doesn’t deserve him, and I gave him everything, and this is how he repays me.” By replacing me with some teacher, the jealousy had mutated into a profound sense of injustice. Sienna truly believed she had been wronged, that something that belonged to her had been stolen.
On October 8th, exactly one week before the murder, Sienna did something unhinged. She created a fake Instagram account posed as a mom named Sarah and messaged Elina asking if she did private tutoring after school. It was a ruse, a way to breach the wall. Elena, being a sweet and helpful person, responded saying she didn’t do private tutoring, but could recommend colleagues who did.
She was polite, professional, but that wasn’t the point. Sienna just wanted to interact with her, to get Elena to respond, to feel some kind of connection to the woman who’d stolen her life. She wanted to see if she could get close. It gave her a sense of power to know she was talking to Elina without Elina knowing who she really was.
On October 10th, Sienna texted Jordan saying, “I just want to talk to her face to face. Make her understand what she’s doing to me.” Jordan, sensing the danger in Sienna’s tone, texted back, “Please don’t do anything crazy. He’s not worth it. Just let it go, Sienna. You’re better than this.” Sienna replied, “I’m not going to do anything.
I just need closure. Closure. That dangerous, nebulous word. People use it to justify all kinds of boundary crossing behaviors. Let that word sink in because 4 days later, Sienna’s idea of closure would leave a young woman dead in a parking lot. October 14th, 2023. A Friday evening. The air was crisp, hinting at autumn.
Elena had finished her work week teaching third graders. It had been a long week of parent teacher conferences and lesson planning and she was ready to unwind. She was heading to a friend’s birthday dinner at a restaurant in Corona called the Olive Mill. She told Matteo about it. He told her to have fun, drive safe, and text him when she got there.
He had his own plans to watch football with friends. Neither of them knew that this mundane Friday night would be their last. What neither Elina nor Matteo knew was that Sienna had been monitoring Elena’s location in real time. Elina had her location visible to friends on Snapchat. It’s a common feature. Snap Map used to see where your buddies are hanging out.
Sienna had made a fake Snapchat account. Added Elina claiming to be a teacher from a nearby district wanting to network. And Elina, friendly, trusting, and unsuspecting, accepted the request. It was the fatal error. Now Sienna could watch Elena’s Bitmoji move across the map.
She had a tracking device right in her hand. At 6:47 p.m., Elena’s location showed she was at the restaurant Olive Mill in Corona. Sienna was at home, sitting on her couch, obsessively refreshing the map, watching the dot stay stationary. At 7:15 p.m., Sienna started getting ready. She didn’t dress for a fight. She dressed for a normal night out.
She put on makeup, fixed her hair, changed into jeans and a black top. She grabbed her purse. Kayla saw her leaving and asked where she was going. Sienna said, “Just out for a drive. Need to clear my head.” Her voice was calm. Too calm. But she wasn’t going for a drive. In her purse, nestled beside her wallet and lipstick, was a Glock 19 handgun.
She had purchased it legally 3 months earlier in July. She told the gun store owner she wanted it for home protection because she lived alone and felt unsafe. She passed the background check. She waited the 10 days. She took the safety course. Everything was by the book. But tonight, that gun had a very different purpose. It wasn’t for protection.
It was for execution. At 7:32 p.m., Sienna got into her car, a silver Nissan Alultima, and started driving toward Corona. It was a 23minute drive from her apartment. Cell phone records and traffic camera footage later confirmed her route. She took the 91 freeway, exited at Main Street, and headed straight to the Olive Mill.
She didn’t speed. She didn’t drive erratically. She drove with the precision of someone who had a destination and a deadline. At this point, what was Sienna planning to do? That became the milliondoll question later at trial. Did she plan to kill Elina or did she want to confront her and things got out of hand? Prosecutors argued she intended to kill her.
Why else bring a loaded gun to a conversation? Why stalk her for weeks? The defense claimed it was for protection and she only wanted to talk, that the gun was a security blanket for her fragile mental state. But for now, let’s focus on the facts of what happened that night. At 8:03 p.m., Sienna arrived at the Olive Mill parking lot. It was a busy Friday night.
Cars were coming and going. People were laughing, walking in groups. Security footage showed her Nissan pulling in slowly, circling the lot twice, clearly looking for someone. She wasn’t looking for a parking spot near the door. She was looking for a specific vehicle. She found Alena’s white Honda Civic parked near the back under a flickering street lamp.
She recognized it from her reconnaissance. She parked four spots down, shut off the engine, and sat there. For 18 minutes, Sienna sat in her car in the dark. 18 minutes. That’s a long time to think. She scrolled her phone. She looked up at the restaurant entrance every few seconds. Imagine the thoughts running through her head, the anger, the jealousy, the rage building for months, now focused into a laser beam. She could have driven away.
She could have called a friend. She could have gone to get a burger. She could have made a different choice. Every second of those 18 minutes was a choice to stay, a choice to wait, a choice to kill. At 8:21 p.m., the restaurant door opened. Elina walked out with two friends. They were laughing, maybe sharing an inside joke from dinner.
Elena looked happy, radiant. She hugged them goodbye, promising to text later. Her friends walked to their car, and Elina walked to her Honda Civic. She fished her keys out of her purse, unlocked the door, and got in the driver’s seat. That’s when Sienna moved. Security footage showed Sienna’s Nissan starting up, backing out rapidly, and pulling up right behind Elena’s car, blocking her in diagonally.
Elena must have been confused at first. She probably checked her rear view mirror, wondering why this silver car was blocking her exit. She waited a few seconds, expecting the car to move, but it didn’t. So, she put her car in park, opened her door, and stepped out to see what was going on. Maybe she thought it was someone who needed help.
Maybe she thought it was a mistake. That’s when Sienna got out of her car. She left her door open. She walked with purpose. According to two witnesses, a married couple, Robert and Diane Chen, who were walking to their car a few rows over. Sienna approached Elina quickly. She was saying something, shouting, but they couldn’t quite make out the words over the ambient noise of the parking lot.
Elena looked confused, squinting in the dim light. Then her face changed. Recognition dawned on her. She’d seen photos of Sienna on Matteo’s old Instagram posts. She knew who this was. The ex-girlfriend, the stalker, the nightmare. Robert Chin testified. He heard Elina say clearly, “I don’t want any trouble.
Please just leave me alone.” Her voice was high, laced with fear. She took a step back toward her open car door. Sienna responded with something angry, a guttural shout still inaudible on the tape, but her body language was aggressive, closing the distance. Elena tried to get back in her car, tried to retreat to safety, and that’s when Sienna pulled out the gun.
The metal glinted under the parking lot lights. Diane Chen screamed. It was a primal sound that cut through the night air. Robert yelled, “Oh my god, she has a gun.” and fumbled to pull out his phone to call 911. Elina held up her hands, palms open, backing away, terrified. Witnesses heard her begging, “Please, please don’t.
You don’t have to do this.” The whole confrontation happened in less than 10 seconds. It was fast, chaotic, and terrifying. Sienna raised the gun. She didn’t hesitate. She didn’t shake. She fired once. The sound was deafening. A crack like thunder. Then twice, three times, four times, five times. The shots echoed off the pavement and the nearby buildings.
Alina Mercer collapsed in the parking lot. She’d been hit four times, twice in the chest, once in the abdomen, once in the shoulder. One bullet missed, lodging in the side of a nearby SUV, shattering the window. Robert Chen was already on the phone with 911, screaming about shots fired and giving the location, his voice cracking with panic.
His wife was crying hysterically, huddled behind a car, having witnessed a murder right in front of her. And then Sienna did something chilling, something that would be replayed in court over and over again. She just stood there for 6 seconds. According to the timestamp on the security footage, Sienna stood completely still, the gun still in her hand at her side, staring down at Elena’s body. She wasn’t looking around.
She wasn’t checking her phone. She was just looking at what she had done. Was it regret? Was it satisfaction? Was it shock? Only she knows. And then she turned, ran back to her Nissan, jumped in, and sped out of the lot, tires screeching, running a red light as she turned onto Main Street and disappeared into the night.
Corona police arrived at 8:24 p.m., just 3 minutes after the first shot was fired. Their response time was incredible, but it wasn’t enough. Paramedics arrived right behind them, sirens wailing, lights painting the parking lot in chaotic reds and blues. They found Elina lying in a pool of expanding crimson, barely conscious, struggling to breathe.
One paramedic, Sandra Lopez, later testified that the scene was heartbreaking. She knelt beside Elina, applying pressure, trying to staunch the flow of blood. Alina looked right at her, her eyes unfocused and dimming, and whispered, “Tell Matteo I love him.” Those were the last words Alina Mercer ever spoke. A message of love in the midst of violence.
Elina was rushed to Corona Regional Medical Center. The ambulance ride was a blur of activity. Paramedics fighting to keep her heart beating. Trauma surgeons were waiting. They worked frantically to save her life, cracking her chest open, massaging her heart, trying to repair the catastrophic damage. But the injuries were too severe.
Two bullets had pierced her lungs, filling them with blood. One had nicked her heart. The damage was irreversible. At 9:17 p.m., 56 minutes after being shot, Alina Mercer was pronounced dead. The doctor stepped back, gloves bloody, heads bowed in defeat. The time of death was called. She was 25 years old. She’d been a teacher for 3 years.
She had plans to go back for her master’s degree in education. She’d booked a vacation to Hawaii for December with Matteo, a trip they had been planning for weeks. She had a family who loved her, students who adored her, a boyfriend who thought she was his future. And now she was gone, a life extinguished, all because a woman couldn’t handle the fact that her ex-boyfriend had moved on.
While Elina was fighting for her life in the ER, detectives were already hunting for her killer. And thanks to the witnesses and cameras, they had a name almost immediately. Robert Chen and his wife gave police a description of the shooter. White woman, mid20s, blonde hair, about 56, and a partial license plate starting with 7J.
But more importantly, security footage captured everything. The car, the shooting, and a clear highdefinition shot of Sienna’s face as she ran back to her vehicle. It was undeniable. It was Sienna Vale. Within 20 minutes of Alina being pronounced dead, detectives identified Sienna Vale as their prime suspect. They ran her plates. They pulled her file.
They knew where she lived. They knew where she worked. They knew about the police report Matteo had tried to file just weeks earlier. The pieces fell into place with tragic ease. At 10:45 p.m., a tactical team of detectives and patrol officers surrounded Sienna’s apartment building in Riverside.
They established a perimeter. They prepared for a standoff. You might think Sienna would have gone on the run, fled to Mexico, ditched the car hidden in a motel. Nope. She was home. She had driven back to her apartment, parked the car in her assigned spot, the murder weapon still inside, gone upstairs, and was sitting on her couch, watching TV.
She was still wearing the same clothes she’d worn to commit murder just 2 hours earlier. [snorts] Officers knocked on the door at 10:52 p.m. Loud authoritative knocks. “Police, open up!” Kayla answered, confused and terrified. She saw the uniforms, the guns drawn. They asked if Sienna Vale was home. Kayla, trembling, said yes and called for her.
Sienna walked out from her bedroom. She saw the officers. According to the arrest report, her face went pale, drained of all color. Detective Sarah Mitchell stepped forward and said, “Sienna Vale, we need to talk to you about an incident in Corona tonight. Are you willing to come down to the station to answer some questions?” At that point, Sienna wasn’t technically under arrest yet.
They wanted to see if she would talk voluntarily. She could have said no. She could have asked for a lawyer immediately, but she didn’t. Instead, she looked at Detective Mitchell and said something that detectives found strange and chilling. I knew you’d come. I knew this would happen. It was an admission of guilt without saying the words.
She grabbed her purse, put on her shoes, and walked out to the police car like she was heading to a routine dental appointment. No fight, no running, just resignation. During the drive to the station, officer Marcus Thompson testified that Sienna was eerily calm. She didn’t cry. She didn’t ask if Elena was okay. She didn’t ask what charges she might face.
She just stared out the window at the passing street lights in silence. At 11:14 p.m., Sienna was taken into interrogation room be she sat down at the metal table, folded her hands in her lap, and waited. What came next was one of the most disturbing interrogations ever covered on this channel. It was a masterclass in police work and a window into a broken mind.
If you’re enjoying this detailed breakdown of the investigation, please leave a like on the video. It helps the algorithm show it to more people interested in true crime. And if you’ve got thoughts on Sienna’s behavior, drop them in the comments. I read every single one. At 11:31 p.m., Detective Sarah Mitchell and Detective Brandon Cole entered the room.
Mitchell sat down a thick folder of evidence on the table with a heavy thud. She looked at Sienna and asked, “Do you know why you’re here?” Sienna looked at the folder, then at the detectives, and said softly, “I think so.” Mitchell pressed, “Why don’t you tell us?” Sienna took a deep breath and said, “It’s about Matteo’s girlfriend, isn’t it?” Note that already.
She referred to Elina as Matteo’s girlfriend, distancing herself from the human being she had just killed, reducing her to a relationship title. Cole leaned in. “Ellina Mercer, do you know her?” Sienna looked him in the eye and said, “Not really. I mean, I know of her, but we’ve never met. That was lie number one, a blatant, easily disprovable lie.
Mitchell leaned forward, her voice serious. She told Sienna that Elina had been shot and had died at the hospital. It was now a murder investigation. She watched Sienna closely for a reaction. According to detectives, Sienna’s face didn’t change. No shock, no gasp, no tears. She just nodded slowly and said, “Okay.
” It was a reaction devoid of empathy, devoid of humanity. Cole asked where Sienna was between 8 and 900 p.m. that evening. Sienna said, “I was home all evening. I didn’t go anywhere. My roommate can confirm.” Lie number two, and a stupid one, because police already had security footage, traffic cam footage, and cell tower data putting her at the scene.
They knew she was lying. They just wanted to see how deep she would dig her hole. Mitchell pulled out a still image printed from the restaurant parking lot camera. It showed Sienna’s silver Nissan with the license plate clearly visible. She slid it across the table and asked, “This is your car, isn’t it, Sienna?” Sienna stared at the photo for a long moment. Her eyes darted around the room.
Then she said, “Someone must have stolen it. I didn’t drive it tonight.” Cole challenged her immediately. So, your car was stolen, driven to Corona, used in a murder, then driven back to your apartment and parked perfectly in your assigned spot, all without you noticing. “And the keys are in your purse right now,” Sienna stammered.
She said she didn’t know how to explain it. She started to sweat. Mitchell pulled out the ace card. Another photo, a clear color shot from security footage of Sienna’s face right before she got into her car to flee. It was unmistakable. Mitchell said, “We have witnesses who saw you shoot Elina. We have footage. We have your phone pings.
We have the texts to Matteo. We know everything, Sienna. Don’t insult our intelligence.” That’s when Sienna finally broke. The facade crumbled. She put her face in her hands and started crying loud, sobbing heaves. But the detectives noted in their reports that they believed these weren’t tears of remorse for Alina.
They were tears of self-pity. tears of someone who realized she’d been caught and her life was over. “I want a lawyer,” Sienna choked out. And just like that, the interrogation ended. The game was up. At 11:58 p.m., Sienna Vale was officially arrested and charged with firstdegree murder.
She was booked into Riverside County Jail, traded her street clothes for an orange jumpsuit, and was placed in a holding cell to await arraignment. Detectives spent the next few days building an airtight case. They didn’t just want a conviction. They wanted to ensure she never walked free again. Cell phone records were damning.
On the day of the murder alone, Sienna checked Elena’s location on Snapchat 73 times. 73. That’s almost once every 10 minutes for 12 hours. She looked at Elena’s Instagram profile 42 times. She googled Olive Mill Corona three times to check the menu and layout and checked Google Maps for directions twice. Forensic analysts recovered deleted search history from her laptop and phone going back months. It was chilling reading.
Two weeks before the murder, she Googled, “How long does a murder investigation take?” Then she searched, “Can you get away with murder if there are no witnesses?” A week before the shooting, she searched sentencing for firstdegree murder California and gunshot wounds survival rate.
This wasn’t a crime of passion or a spur-of-the- moment mistake. This was premeditated, calculated research murder. She had been studying for this like a final exam. Then there were the text messages, thousands of them. Investigators recovered deleted texts from the cloud where Sienna expressed increasingly violent thoughts about Elina to her few remaining friends.
“I just want her to disappear,” she wrote to Jordan. “Sometimes I think about what it would be like if she just didn’t exist. Like if she got in a car accident or something. She doesn’t deserve to be happy. She doesn’t deserve him. He’s mine.” Jordan later testified she tried to talk Sienna down, telling her to seek therapy, but Sienna was too far gone in her delusion.
The most damning evidence came from Sienna’s car. 2 days after the murder, forensics executed a search warrant on the Nissan Alultima impounded in the police lot. Inside the center console, nestled under some receipts and gum wrappers, they found the Glock 19 used in the shooting. Sienna didn’t even get rid of it.
She didn’t toss it in a river or bury it. She just put it back in the console like it was a pair of sunglasses. Ballistics tests confirmed the bullets found in Alena’s body matched that gun perfectly. Gunshot residue was found on the driver’s side door handle, the steering wheel, and a black denim jacket found in the back seat.
The same jacket seen in the security footage. Elena’s blood was found on the passenger side of Sienna’s car, likely transferred from Sienna’s shoes or clothes. Sienna’s DNA was found on a Starbucks cup recovered at the crime scene near where her car had been parked. Witnesses confirmed a blonde woman in a silver. Nissan had been drinking Starbucks while waiting in the lot.
Detectives interviewed everyone connected to the case to build a complete picture of the timeline. Matteo Cruz was devastated. When police interviewed him, he broke down. He told detectives he had no idea Sienna was still that obsessed. He thought she’d moved on because of her social media posts. He blamed himself for not taking the stalking more seriously, for not pushing harder for a restraining order, for posting that photo of the barbecue.
The guilt was eating him alive. Kayla provided crucial testimony about Sienna’s increasingly erratic behavior at home. She told police about the shrine-like collection of photos Sienna kept, the way she would talk to herself, muttering curses against Elina. The day before the shooting, Kayla found Sienna sitting in the dark in the living room, staring at her phone screen, which was illuminated with Elena’s face.
When Kayla asked if she was okay, Sienna looked up with what Kayla described as dead, empty eyes and said, “Some people just take and take and never give anything back. It’s time to take back what’s mine.” Kayla didn’t think much of it then, assuming it was just drama. Less than 24 hours later, Alina was dead.
6 days after the murder, the district attorney officially charged Sienna with firstdegree murder, use of a firearm in the commission of a felony, and stalking. Because of the special circumstance of lying in waiting in the parking lot for 18 minutes, she was eligible for life in prison without the possibility of parole.
Her arraignment was set for November 2nd. Normally, a case this clear-cut would end in a plea deal to avoid the trauma of a trial. The evidence was overwhelming, but Sienna’s lawyer, a public defender named Marcus Webb, decided to go to trial. His strategy was to claim it was a crime of passion, to try and get the charge knocked down to seconddegree murder or manslaughter.
He planned to argue that Sienna intended to confront Elina, not kill her, that she brought the gun for protection because she was paranoid and mentally unstable, and that the confrontation escalated into a catastrophic mistake in the heat of the moment. The case became national news. It had all the elements the media loves. A love triangle, a pretty killer, a tragic victim, social media stalking.
Some people on Tik Tok and Twitter actually started fan pages for Sienna, claiming heartbreak drove her to madness and expressing sympathy. She did it for love, some comments read. But most people rejected that narrative entirely. Heartbreak doesn’t make you a murderer. Millions of people get dumped every day.
Millions of people get cheated on or replaced. They cry. They eat ice cream. They go to therapy. They listen to sad music. They don’t buy a gun and shoot someone five times. The crime of passion defense felt like an insult to true victims of domestic violence. Elena Mercer’s family planned her funeral. It was held at a local church packed to overflowing.
Her parents, Carmen and Victor, gave a press conference afterwards, holding on to each other for support. They spoke about their daughter as a light in the world, a born teacher who loved children. They said that jealousy and hate aren’t love, they’re evil. Sienna Vale didn’t love Matteo, Victor said, his voice shaking with grief.
She wanted to possess him, and she destroyed our lives to do it. Students made cards and drawings for Miss Mercer. One little girl drew Elena with angel wings and wrote, “Miss Mercer is teaching angels now.” A memorial was set up outside Riverside Elementary School with flowers, teddy bears, and candles. Matteo visited every day for two weeks, sitting there on the curb for hours, crying, staring at photos, wondering what he could have done differently.
Sienna caused ripple effects that destroyed families and communities because she couldn’t let go because she felt entitled to someone else’s life. She didn’t just kill Elina, she killed the person Matea was. She killed the peace of mind of an entire community. Then came the jail phone calls. In late November, prosecutors obtained recordings of Sienna’s calls from jail.
Inmates are told their calls are recorded, but many forget or don’t care. In one call to her brother, Tyler, Sienna said, “I know everyone thinks I’m a monster. I see what they say on the news, but I gave him everything. Tyler, I gave him my soul. And she just walked in and took it all like I never existed. Someone had to make her understand.
Someone had to stop it. Even after killing Elina, sitting in a jail cell, Sienna still thought she was the victim. She still framed her actions as a necessary intervention, a corrective measure. She showed zero remorse for Elina, only resentment. A clinical psychologist hired by the prosecution later evaluated Sienna.
He testified that she showed clear signs of narcissistic personality disorder and obsessive behavior patterns consistent with a rodamomania, a delusion where a person believes another is destined to be with them. But he was clear. She knew right from wrong. She was not legally insane. She made choices. None of her psychological issues excuse the calculated execution of an innocent woman. The trial began in March 2024.
Jury selection took 3 days to find 12 impartial jurors who hadn’t been swayed by the media coverage. On March 21st, opening statements began. The people of the state of California versus Sienna Marie Vale. The courtroom was packed. Every seat was taken. Elena’s family sat on the prosecution side.
Her parents, her younger sister Sophia and Mateo Cruz, who looked like a ghost of his former self, gaunt and pale. On the defense side sat Sienna’s parents and brother, looking miserable, heads bowed in shame and disbelief. They had lost their daughter, too, in a different way. Sienna walked in wearing a conservative navy blouse and black pants, her hair pulled back in a modest ponytail, minimal makeup.
She looked like a librarian or a school teacher. It was a clear strategy to look sympathetic, harmless, but photos taken that day showed her looking more annoyed than remorseful. She scanned the room with a detached curiosity. Prosecutor Michael Chen delivered a powerful opening statement. He told the jury the case was about obsession, entitlement, and jealousy.
It was about a woman who believed if she couldn’t have the man she wanted, no one else could either. He walked through the timeline. Sienna and Matteo’s relationship, the breakup, Sienna’s escalating stalking, the fake accounts, the drivebys. He said Sienna tracked Elina like a hunter, followed her, waited for her in the dark, and when Elina walked out of the restaurant happy and unsuspecting, Sienna shot her five times.
He emphasized it wasn’t passion. It was premeditated murder. He promised to show the jury the security footage, the texts, the Google searches, the gun purchase records. The defense attorney, Marcus Webb, had a harder job. He admitted Sienna killed Alina. There was no point denying it with the video evidence.
Instead, he argued the key question was intent and state of mind. He painted a picture of a fragile young woman broken by heartbreak, abandoned by her support system, spiraling into a mental health crisis. He argued she went to the Olive Mill just to talk, to get that closure she texted about. He claimed she brought the gun only for protection because she was paranoid living alone.
He said the confrontation escalated, words were exchanged, panic set in, and a tragic mistake occurred. He urged the jury to see the human being behind the act and consider a lesser charge. The prosecution’s case took two weeks and called 43 witnesses. Detective Mitchell took the stand and detailed the investigation, the arrest, and Sienna’s lies.
During interrogation, forensic experts explained the ballistics and DNA evidence, leaving no doubt who pulled the trigger. Digital forensics experts presented the search history and phone location data, projecting the how to get away with murder searches on a large screen for the jury. It was a mic drop moment. Eyewitness Robert Chin testified.
He recounted the screaming, the begging. He said, “The victim was backing away. She had her hands up. She was surrendering.” And the defendant just kept shooting. Diane Chen corroborated his story and added a chilling detail. She said after the shooting, Sienna stared down at Elena’s body with a look that wasn’t panic, but satisfaction.
She said it looked like Sienna was admiring her work. The defense tried to challenge their memory, suggesting it was dark and chaotic, but their testimonies matched the security footage perfectly. Then came the video. The jury watched the parking lot security footage. The courtroom fell into a heavy, suffocating silence. You could hear a pin drop.
On the screen, the silver Nissan blocked the white Civic. The figures moved. the flashes of light from the gun muzzle, the figure crumpling to the ground. Elina’s mother broke down sobbing and had to be helped out of the room. Matteo put his head in his hands, shaking. Some jurors looked away, unable to watch the moment of death.
It was real, raw, and undeniable brutality. Jordan testified about Sienna’s obsession and the disturbing texts. She read aloud the messages where Sienna wished death upon Elina. Gabriella testified how Cien posed as a teacher to gather information, manipulating her kindness. Then Elena’s parents gave victim impact statements, usually reserved for sentencing, but allowed in part here to establish Elena’s character.
They spoke about losing their daughter for something so senseless. Even Sienna’s parents looked devastated, weeping silently. The defense presented their case. They called mental health experts who testified about Sienna’s depression and anxiety. They called character witnesses who spoke about Sienna’s kindness to dental patients, trying to show she wasn’t a monster.
But on cross-examination, the prosecutor dismantled these witnesses, asking if kind people hunt down innocent women and shoot them. The prosecution’s rebuttal witness. A forensic psychiatrist argued that Sienna’s Google searches showed clear planning and her actions after the shooting.
Fleeing, hiding the gun, lying to police showed she had a functioning consciousness of guilt. She knew exactly what she did and she knew it was wrong. Sienna did not testify. It was too risky. Her lack of remorse would have likely alienated the jury further. The defense rested. Closing arguments began on April 4th.
Prosecutor Chin hammered home the premeditation. He listed the steps, buying the gun, tracking the location, waiting for 18 minutes, blocking the car, firing five times. He argued you don’t fire five shots in self-defense or heat of passion. You fire five shots when you intend to ensure death. She wanted to erase Elina, Chen said, and she did.
The defense repeated that Sienna was a broken girl who made a terrible mistake in a moment of madness, begging for mercy. The jury deliberated for only eight hours. It was quick. They reached a verdict. The courtroom filled again. The air was thick with tension. Sienna was brought in, looking pale, her hands trembling for the first time.
Her parents held hands, praying. Alina’s family waited across the aisle, clutching photos of Alina. The judge asked for the verdict. The jury forperson stood up and read. We the jury find the defendant Sienna Marie Vale guilty of firstdegree murder. A gasp went through the room. We find the defendant guilty of the special allegation of personal and intentional discharge of a firearm causing death.
We find the defendant guilty of felony stalking. The courtroom erupted. Elena’s family cried. A mix of relief that justice was served and fresh grief that it wouldn’t bring her back. Matteo wept openly. Sienna’s mother screamed, “No, no.” A sound of pure anguish. Sienna didn’t cry or scream. She just stared ahead, blinking rapidly like she couldn’t process the reality of the words.
As she was led away in handcuffs, she finally turned and mouthed, “I’m sorry to” to her mother. Not to Alina’s family, to her mother. The sentencing was set for May 15th, 2024. The verdict made national headlines. Most people supported it. Some online discourse continued about mental health, but the consensus was clear. Mental illness is not a free pass for violence.
At sentencing, the emotions were raw. Elena’s sister Sophia spoke. She talked about losing her best friend, about the empty chair at holiday dinners, about the wedding Elina would never have, the children she would never teach. “Sienna didn’t just kill my sister,” Sophia said, looking directly at Sienna. “She killed a part of all of us.
” Mateo spoke about his guilt, his voice breaking. “He turned to Sienna and said, I blame myself every day, but I know the choice was yours. You chose to stalk. You chose to bring a gun. You chose to pull the trigger. You took the best person I ever knew because you couldn’t handle rejection. Judge Thornton addressed Sienna before passing sentence.
He described her actions as a calculated, coldblooded, and premeditated campaign of terror that ended in the senseless murder of an innocent young woman. He noted that throughout the trial, Sienna showed more concern for her own fate than for the life she took. You are a danger to society, the judge said, and you have forfeited your right to live in it.
Sienna was sentenced to life in prison without the possibility of parole, plus an additional 25 years to life for the firearm enhancement. It was the maximum sentence allowed by law. She would leave the courtroom in chains and never walk free again. Sienna broke down as she was led away, her legs giving out, deputies having to support her.
Her mother begged the judge for mercy that couldn’t be given. Her father sat in silence, head in his hands, but it was over. The gavl had fallen. As of today, Sienna Vale is incarcerated at the Central California Women’s Facility in Chailla, California. She’s 27 years old. She is surrounded by concrete walls and barbed wire. She will grow old there.
She will die there. She filed an appeal in August 2024 claiming ineffective counsel and insufficient evidence for firstdegree murder, but the appeal was denied. The justice system affirmed the verdict. Elena’s family has tried to find meaning in the tragedy. They established the Alina Mercer Memorial Scholarship for students pursuing teaching careers, helping future educators follow in Elena’s footsteps.
Riverside Elementary planted a cherry blossom tree in her honor near the playground where she used to watch her students. Students still remember Miss Mercer, the teacher with the bright smile who made them laugh and made learning fun. A plaque rests at the base of the tree. A life cut short. A community forever changed.
All because someone couldn’t let go. So, what can we learn from this tragedy? It’s easy to look at Sienna as a monster and in her actions she was. But psychologically she was a person who let her insecurities and entitlement metastasize into lethal obsession. She showed signs of obsessive attachment, narcissistic tendencies, and an inability to regulate her emotions.
But lots of people have issues. Lots of people get their hearts broken. They don’t hurt anyone. The difference is accountability. Recognizing you need help and getting it before you spiral. Sienna had so many offramps. She could have gone to therapy when her friends suggested it. She could have listened to Jordan.
She could have blocked Matteo’s social media for her own sanity. She could have channeled her pain into a new hobby or career. But she chose obsession over recovery every single time. She chose revenge over moving on. And that choice is what makes her responsible. If you’ve been in Sienna’s position, heartbroken, jealous, feeling like your world has ended, recognize the warning signs in yourself.
Are you constantly checking your ex’s social media? Are you driving past their house or workplace? Are you creating fake accounts to monitor them? Are you feeling rage toward their new partner who has done nothing to you? Are you fantasizing about revenge? If that’s you, step back. Get professional help. Talk to a therapist. Join a support group.
Delete the apps. Do anything except what Sienna did. Heartbreak is temporary. It heals. Prison is forever. Death is forever. And if you’ve been in Alina’s or Matteo’s position, dating someone whose ex won’t let go, take the threat seriously. Document everything. Screenshots, logs, witness accounts.
Tell people what’s happening. Don’t minimize it to be nice. Get a restraining order if necessary. Even if it’s hard, push for it. Elena didn’t know the full extent of Sienna’s obsession until it was too late. Don’t make that mistake. Your safety matters more than seeming dramatic or paranoid. Trust your gut.
If something feels dangerous, it probably is. This case is a stark, brutal reminder that love turns toxic when mixed with obsession, entitlement, and a refusal to accept reality. Sienna destroyed three families that night. Elena’s family lost a daughter and sister, a hole that will never be filled. Matteo lost the woman he loved and carries a burden of guilt he doesn’t deserve.
And Sienna’s family has to live with the fact that their daughter, the girl they raised and loved, became a murderer. All over breakup, all because someone couldn’t move on. Rest in peace, Alina Mercer. You deserved so much better. You deserved a long life full of teaching, travel, and love. We remember you not just as a victim, but as the bright light you were.
So that’s the tragic, infuriating case of Sienna Vale and the murder of Alina Mercer. What do you think? Was the life sentence appropriate? Should mental health have been considered differently or did she get exactly what she deserved? Drop your thoughts in the comments below. I’m really curious to hear your take on the closure defense.
If you’re new here, welcome to Women Justice Files. We cover cases everyday, deep divies into the psychology, investigation, trial, everything. We don’t sensationalize. We don’t glorify. We try to understand what happened and why, so maybe we can spot the signs next time. If you found this case compelling, please hit like, subscribe, and turn on notifications so you never miss a upload.
Until then, stay safe, pay attention to red flags, trust your instincts, and remember, if someone can’t accept a relationship is over, that’s not love. That’s danger. I’ll see y’all next day.
