LOS ANGELES (AP) — Los Angeles detectives are trying to determine a motive for the slaying of a vocational school instructor who was allegedly shot by a student during a class for security guards.

Police Lt. Paul Vernon said Thursday that 22-year-old Law Thien Huynh of Gardena argued with the instructor immediately before leaving the classroom and returning with a firearm. Vernon says the student shot the teacher at near point-blank range Wednesday afternoon.

Students at Coast Career Institute said that after 44-year-old instructor Roberto Herrera was shot, the gunman put the weapon down, told classmates to call 911 and walked outside to smoke a cigarette.

Classmate Jermaine Walter said that Huynh often asked questions in class about shooting and killing people.

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