LOS ANGELES, CALIFORNIA (BNO NEWS) -- A school teacher on Wednesday was killed by one of his students in downtown Los Angeles, California, KTLA television reported on Thursday.

Roberto Herrera, 44, was shot by a 22-year-old Gardena man following an argument. The student, Thien Huynh, left the class and went to the restroom. Moments later, he returned with a pistol and shot him multiple times.

The fatal incident took place at around 4:00 p.m. local time at the Coast Career Institute on South Hill Street. The suspect was detained shortly after while he was calmly smoking cigarettes nearby.

Herrera worked as a security guard and also taught the 24-week class for the last three years. The classroom had 13 students who witnessed the murder and described Herrera as a very nice guy.

However, witnesses said that Huynh had been singled out negatively in class by his instructor on previous occasions. Besides Herrera, the suspect did not shoot at anybody else.

A criminal investigation was launched by LAPD and a motive has not been established yet.

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