SAN DIEGO (FOX 5/KUSI) — The sentencing of a man convicted of first-degree murder in the death of his ex-girlfriend's fiancé, a popular Cathedral Catholic High School teacher, has been delayed after he came down with an unidentified illness. Jesse Alvarez, 34, was found guilty by a jury last March for gunning down Mario Fierro as he was leaving his North Park home to head to work on the morning of Feb. 1, 2021. Prosecutors argued Alvarez laid in wait outside Fierro's home to ambush him in an attack he planned for two months after he learned of his engagement to his ex-girlfriend, Amy Gembara. Gembara was also a teacher at Cathedral Catholic High School at the time. Police: 19-year-old fatally shot in Lincoln Park Alvarez, who testified during the trial, described having an "unhealthy obsession" with Gembara before the murder took place. At the time, it had been more than three years after the two had broken up. Prosecutors said Alvarez stalked her, prompting her to move, change her number and seek a restraining order. When he learned of her engagement, he searched on Google how to kill Fierro, including things like how to hire a hitman. FILE: Mario Fierro. (Courtesy of Catholic Diocese of San Diego) Alvarez's defense attorneys argued the murder was not premediated, instead occurring out of self-defense in a scuffle with Fierro when he went to the teacher's home to introduce himself. Fierro was shot six times, including four times in the head, according to prosecutors. A new date for Alvarez's sentencing has not been set. He faces life in prison without the possibility of parole.