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The story of Jesse Alvarez’s dangerous infatuation is one that spiraled out of control, ultimately leading to tragedy.
For several months, Alvarez was consumed by an obsession with his former girlfriend, Amy Gembara. In a relentless pursuit to keep tabs on her, he began by probing her friends for details through social media. His fixation grew as he sought employment at the high school where Gembara worked, even going so far as to impersonate a former student in a bid to be near her on campus.
This unhealthy obsession reached a deadly climax on February 1, 2021. On that day, Alvarez ambushed and fatally shot Gembara’s fiancé, Mario Fierro. Fierro, a respected athletic coach and teacher, was gunned down in a barrage of bullets as he was heading to work, ending his life tragically and abruptly.
The chilling tale of this murder was revisited in an episode of Oxygen’s series A Plan to Kill, which aired on March 15. The episode delved into the details of Alvarez’s desperate and calculated actions in his attempts to reclaim a love that had slipped away.
Detective Chris Leahy, reflecting on the case, described the grim reality of Alvarez’s actions: “He was watching, waiting,” he said. “And it was clear that this murder was premeditated.”
Mario Fierro Shot to Death Outside Car
Cathedral Catholic High School was resuming in-person classes the morning of Feb. 1, 2021 amid the COVID pandemic—but one teacher would never return.
Fierro was gunned down outside his San Diego apartment as he left for work that day. Officers found the 36-year-old lying in a pool of blood behind his Mini-Cooper after getting calls from concerned neighbors who heard a series of shots.
“It definitely appeared, based on how the scene was initially, that there was some element of an ambush,” San Diego Police Det. Ricardo Escalante recalled. “It was a surprise attack.”
One witness reported seeing Fierro standing outside by the car fighting with another man who pointed a white object—she believed to be a thermometer—at his head around the time of the shooting. As she drove away, she saw the suspect jump into a hatchback car and drive off.
Using that witness’ account, detectives were able to track down surveillance footage which showed a dark-colored hatchback car leaving the crime scene shortly after the gunshots.The same vehicle was seen arriving in the area around 6 a.m., leading investigators to conclude that the killer had been laying in wait.
Detectives Learn Amy Gembara Had a Stalker
Detectives caught another break early into the investigation when they were approached at the crime scene by a Homeland Security investigator, who told them that Gembara, his cousin, had asked him to go to the apartment after Fierro failed to show up for work that morning.
He told detectives that Gembara had been a victim of a stalker and he believed it was possible that Alvarez, her former boyfriend, may have had something to do with the attack.
Fearing that Gembara could be in “immediate danger,” Leahy drove to the high school, contacting Deputy District Attorney Ramona McCarthy along the way. For months, McCarthy—who worked in the stalking unit—had been working with Gembara to try to keep her safe as she tried to take out a restraining order against her ex.
According to McCarthy, Gembara dated Alvarez before Fierro, but she ended the relationship two years earlier after she noticed “red flags” like controlling and manipulative behavior.
Amy Gembara Details Ex Jesse Alvarez’s Obsessive Behavior
Once at the school, Leahy delivered the difficult news to Gembara that her fiancé was dead.
“When I arrived at the school, Amy was seated in the principal’s office, and I told her that Mario had died, and Amy began screaming and wailing,” he recalled. “She fell to the ground, and she immediately started saying, ‘Jesse did it. Jesse did it.’”
She told investigators that after breaking up with Alvarez, he began following her around San Bernardino, where they both lived at the time. Hoping for a fresh start, she’d moved to San Diego, gotten a job at Cathedral Catholic High School and met Fierro, a beloved teacher and coach at the school known for his big smile and love of sports.
But Alvarez wasn’t willing to let her go, calling her all the time and reaching out to her friends on social media to try to get information on her whereabouts.
Jesse Alvarez Is Apprehended at His Brother’s Home
After identifying Alvarez as the likely suspect in the shooting, investigators tracked him to his brother’s home in San Diego about 10 minutes away from the crime scene. They observed a dark colored hatchback—registered to Ryan and seemingly matching the vehicle from the surveillance footage—in the driveway of the home.
Alvarez was apprehended and brought to the station for questioning. Meanwhile, a separate set of investigators spoke to his parents and brother, all of whom reported that Alvarez had left early that morning, taking Ryan’s vehicle without permission.
After obtaining a search warrant to search the home, detectives found a handgun and rifle registered to Alvarez, both painted white.
“The fact that the weapons were painted white was incredibly important to the investigation,” Escalante explained, “because there was a witness that had described the suspect using a white item and placing it to the victim’s head.”
They also found Cathedral Catholic High School-themed clothing in his closet, suggesting that Alvarez may have been using the clothing to try to blend in at the school.
Jesse Alvarez Is Arrested After Claiming the Shooting Was in Self-Defense
Back at the station, Alvarez initially claimed that he had never dated Gembara, telling detectives that she had wanted a relationship but he was never interested.
“Then he starts to say well, she may have believed we dated, that she has this histrionic disorder where she thinks relationships are closer than they are,” San Diego Police Detective Ron Newquist said. “He was very comfortable lying to the two homicide detectives sitting right in front of him.”
However, when he was confronted with the evidence against him, Alvarez changed his story, saying he’d just gone to Fierro’s home because he was worried he was mistreating Gembara. He claimed that Fierro had lunged at him and begun to attack him and he shot Fierro six times in self-defense.
“This was all very fast,” he told detectives. “And that’s why I kind of just kept firing kind of aimlessly.”
Detectives didn’t believe his account and he was arrested and charged with murder.
Evidence Shows Jesse Alvarez Displayed “Unwavering Commitment” to Kill
As the trial loomed, investigators continued to build their case and learned that Alvarez had been following over 470 social media accounts associated with the high school—including one that announced Gembara and Fierro’s engagement six weeks earlier.
As McCarthy explained, “The love of his life, Amy, his ex-girlfriend, is now engaged to Mario Fierro and from that point we believe he shifted his focus to stalking Mario.”
Detectives learned he’d conducted extensive searches on Fierro’s background and Googled information on how to kill someone.
According to Newquist, “Jesse was enraged to the point where he could not stop himself.”
They also learned that he’d posed as a Cathedral Catholic student online and went to the campus to talk to students and faculty while claiming to be alumni. He’d even applied for a job at the school and gotten an interview, using the time he spent on campus to take photos of Amy’s classroom and the layout of the building. Four days after the interview, he bought the firearms and began training at a gun center.
“In my 15 years as a homicide investigator, I have never seen a case that showed more premeditation, more planning and unwavering commitment to commit a murder,” Newquist said. “Jesse had several opportunities to back out of this, but he chose to go to Mario’s house, locate him and gun him down in his driveway.”
Alvarez was convicted of first-degree murder with a special circumstance of lying in wait in 2024 and sentenced to life without the possibility of parole along with an additional 25 years.
To learn about the lengths others are willing to go to kill, watch A Plan to Kill Sundays at 7 p.m. ET/PT on Oxygen.