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SAN DIEGO — A 30-year-old man suspected of fatally shooting a high school teacher and coach outside of his North Park home was in jail Tuesday.

Authorities arrested Jesse Alvarez, a San Diego resident, at a home in Serra Mesa Monday night. San Diego police said he was booked into San Diego Central Jail on suspicion of murder.

Shortly after 7 a.m. Monday, police found Mario Fierro, 37, unresponsive on a sidewalk near 4500 Kansas Street. Police said he was shot once in the head. He died at the scene despite life-saving efforts.

Police did not say if Alvarez knew Fierro or what the motive for the shooting was. Sources told FOX 5 Alvarez was a former boyfriend of Amy Gembara, Fierro’s fiancée. Court records show Gembara filed for a domestic violence restraining order against Alvarez on Dec. 31, 2019, which a judge dismissed.

Gembara said in the document that she tried to break up with Alvarez but he kept stopping by, harassing her and trying to get back together. She said Alvarez was calling her 20 to 30 times from unknown numbers.

“I was fearful for my safety, [Alvarez]’s attempts to restrain me, attempted break-in at my residence and threats of suicide after we broke up,” the document says. “I need this protective order for my safety and security … I’m extremely afraid he will harm me.”

When officers got to Kansas Street Monday morning, the trunk of Fierro’s car was ajar, a sign police say Fierro was heading to work. He taught social science at Cathedral Catholic High School and was the athletic director at Notre Dame Academy.

The Catholic Community Foundation of San Diego announced Tuesday that a scholarship fund was created in Fierro’s honor. He was a product of Catholic schools and graduated from University High School, the predecessor to Cathedral Catholic High School in 2002. He returned to CCHS in 2016 as a teacher and football coach.

CCHS canceled classes until Thursday and was providing grief counseling to students and staff. The campus community gathered Monday evening at St. Therese of Carmel Catholic Church to pay tribute to Fierro.

“It was incredible,” Mario’s younger brother Rueban Fierro said of the crowds at Monday night’s vigil. “There were people there I had never even heard of.”

Fierro’s family said Fierro started coaching football right out of college, partly because it gave him the chance to work with kids in the Catholic community.

“He was a mentor, teacher, and an all-around good person,” Mario’s younger sister Daniella said. “A great person to get advice from, and a great person who was good to students and family as well.”

Alvarez is scheduled to be arraigned Feb. 19.