Cathedral Catholic teacher-slaying suspect searched ‘How to kill your ex's fiance': San Diego DA

A man accused of gunning down his ex-girlfriend's fiance in North Park carried out the crime in a fit of jealousy and obsession, a prosecutor told jurors Monday, but a defense attorney insisted the shooting was committed in self-defense.

Jesse Milton Alvarez, 33, is charged with killing 37-year-old Mario Fierro, a Cathedral Catholic High School teacher, outside Fierro's home as the victim was preparing to go to work on the morning of Feb. 1, 2021.

Prosecutors allege Alvarez methodically planned the killing over the course of several weeks, waited outside Fierro's home for about an hour until the victim left his residence, then shot him six times at close range. Fierro died at the scene.

Deputy District Attorney Ramona McCarthy told jurors the killing stemmed from an unhealthy obsession with Fierro's fiancee, whom Alvarez had previously dated for more than three years.

Describing Alvarez as "jealous, obsessive, and possessive," the prosecutor said that following their break-up, Alvarez proceeded to repeatedly contact the woman, despite her telling him she did not want to speak with him or continue the relationship. Due to those unwanted contacts, which included showing up at her home unannounced and using alternate phone numbers and social media accounts to circumvent her attempts to block his communications, she unsuccessfully sought a restraining order.

After a judge declined the restraining order request, Alvarez's attempts to contact her persisted, McCarthy said, including through multiple attempts to secure a job at Cathedral Catholic High School and mailing letters to new home addresses that the woman did not share with him.

In December 2020, Fierro and the woman got engaged and the school publicly announced it in a celebratory social media post that Alvarez discovered.

McCarthy said upon learning of the engagement, Alvarez began planning Fierro's "execution."

Along with taking courses on how to shoot firearms, Alvarez made a series of internet searches that highlighted his intent to kill Fierro, the prosecutor said.

Those included searches for hiring hitmen, where to shoot someone in the head to ensure death, how to shoot someone without leaving forensic evidence, and how to "commit the perfect murder."

One search made less than a week after the engagement announcement read simply, "How to kill your ex's fiance."

McCarthy alleged Alvarez also searched Cathedral Catholic High School's schedule in order to determine when the school would be transitioning from pandemic-era remote learning to on-campus instruction. The first day of the school's return to on-campus instruction was Feb. 1, the date of Fierro's death.

"His ex was in love, but it wasn't with him," McCarthy told jurors, "It was with Mr. Fierro. And that is why he is not alive today."

Defense attorney Kerry Armstrong told jurors Alvarez has high-functioning autism and is "extremely religious," two aspects of his life that heavily informed his actions leading up to the shooting.

Armstrong conceded that Alvarez did not handle the end of the relationship well, but said his autism prevents him from adequately grasping social cues or from recognizing that his behavior was inappropriate.

The attorney said Alvarez was "crushed" and "heartbroken" upon discovering his ex's engagement, but said his true issue with the new relationship began with a picture posted on social media in which Fierro and Alvarez's ex-girlfriend were seen having alcoholic drinks.

Armstrong said the picture bothered Alvarez because of his client's religious nature and he was concerned that Fierro "might lead her down the path of substance abuse." The attorney said Alvarez "believed it was his role to protect her" and wanted to speak with Fierro for that reason.

The defense attorney said Alvarez, who is expected to testify on his own behalf, would explain to jurors that on the morning of Feb. 1, he tried to speak with Fierro, who became very upset upon seeing Alvarez.

Armstrong alleged Fierro said something to the effect of, "I know who the [expletive] you are. I'm going to [expletive] kill you. Get out of here."

Armstrong said Fierro then began punching Alvarez, prompting Alvarez to produce his gun and tell him to stop. Fierro continued advancing and "fearing for his life, he began to shoot," Armstrong said.

The defense attorney denied any plan to murder Fierro, and said the gun was purchased before Alvarez was even aware Fierro had been dating his ex-girlfriend.

Alvarez faces life in prison without the possibility of parole if convicted of first-degree murder, plus a special-circumstance allegation of lying in wait.

The trial, which is underway at the San Diego Central Courthouse, is expected to last about two to three weeks.