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Tuesday update: Police have arrested a 30-year-old man in connection with Mario Fierro’s killing.

SAN DIEGO – A community is mourning the loss of a high school teacher and coach who was gunned down outside of his North Park home.

Mario Fierro, a 37-year-old teacher at Cathedral Catholic High School, was honored by his fellow staff and students late Monday. Authorities found Fierro just after 7 a.m. Monday unresponsive and with a bullet wound on a sidewalk in the 4500 block of Kansas Street.

Students and staff at Cathedral Catholic High School gathered late Monday to pay tribute to Mario Fierro. Authorities found Fierro, 37, just after 7 a.m. Monday unresponsive and with a bullet wound on a sidewalk in the 4500 block of Kansas Street.

The trunk of his car was found ajar, which police say was a sign Fierro was headed to work.

“(He was) just the best, the best human being — just the best, best person,” said Katie Wilson, a drama teacher at the high school.

Among those in attendance, it was a sad and shocking day to lose a beloved teacher.

“I broke down in tears,” senior student Colman Smith said. “It was the worst news I could have gotten.”

Guidance counselors were available Monday to support grieving members of the school community. Cathedral Catholic also will be closed Tuesday, according to Principal Kevin Calkins.

Those who worked with Fierro said he was “Mr. Popular” and will be impossible to replace.

“I hate the word ‘unprecedented,’ but this is another unprecedented situation,” Calkins said, “and, you know, we’re going to be together. We’re going to rely on our faith and one another.”

“There was no other coach that just lived and breathed every move on the field, every success,” Wilson said. “Watching him on the sidelines was worth attending any game — that’s why I would go to watch.”

Students say Fierro believed deeply in faith, put his heart into teaching history and coaching football at the same school he once attended in the 2000s.

“If we get a season this year, which I hope we do, we’ll play for him and his name,” Smith said.