RELATED: All 3 San Francisco UPS shooting victims identified
They also released our first photo of the shooter, Jimmy Lam, taken after, from a previous brush with the law.
Police say Lam killed three co-workers in the June 14 shooting at a UPS facility in San Francisco -- Mike Lefiti, 46, Benson Louie, 50, and Wayne Chan, 56.
Police gave ABC7 News more details on what happened last week in the deadly shooting spree that lasted less than 10 minutes and began during a morning staff meeting.
"As the meeting was taking place, Mr. Lam produced an assault-type pistol... without warning or saying anything. He immediately shot Benson Louie. After shooting Mr. Louie, Mr. Lam then shot Wayne Chan," said an SFPD spokesperson.
Police released a photo of Lam, an older booking photo, they say came from some previous, non-violent contacts with the law.
They also showed ABC7 News the weapons he had on him, a pistol they say was stolen from Napa, and a MAC-10 with 30-round magazine they say was stolen from Utah.
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Magazines over 10 rounds are illegal in California and police say Lam fired 20 shots.
Police say his third victim, Lefiti, was shot outside in the street multiple times without saying a word, he then re-entered the building where it took police about two minutes to find him.
The shooter's death leaves police with questions about what motivated the killings. Police say they seized cellphones, computers, and a journal from his house in hopes of learning what he was thinking. But they've already concluded the shootings were targeted, based on witness reports and video of Lam going after the victims while leaving other employees alone.
Friday, the union confirmed that UPS has brought in workers from the East Bay, South Bay, and Nevada to cover for employees taking medical and bereavement leave in the wake of the shootings.
Click here for more information about the shooting.