A UPS employee who had recently filed a grievance opened fire Wednesday inside one of the company's San Francisco warehouses, killing three people before fatally shooting himself, as panicked workers ran out onto the streets, police said.

The gunman, wearing a UPS uniform, opened fire on three fellow employees and then "turned the gun on himself," company spokesperson Steve Gaut said. Police identified San Francisco resident Jimmy Lam, 38, as the gunman. Two others were wounded.

"This is a tragedy that has touched many lives today," Assistant Police Chief Toney Chaplin said.

Police on Wednesday swarmed a duplex in San Francisco's Inner Richmond neighborhood believed to be the home of UPS shooting suspect Jimmy Lam. Jaxon Van Derbeken reports.

Police identified the victims killed in the rampage late Wednesday as Wayne Chan, 56; Mike Lefiti, 46, and Benson Louie, 50. Police said their families have been notified.

Joseph Cilia, an official with a Teamsters Union local that represents UPS workers in San Francisco, told The Associated Press Lam had filed a grievance in March complaining about working excessive overtime hours.

Still, Cilia said Lam wasn't angry, and he could not understand why he would open fire on fellow drivers at a morning meeting. Cilia says witnesses told him Lam appeared to specifically go for the drivers who died, chasing at least one of them out of the building.

"I never knew Jimmy to not get along with people," Cilia said. "Jimmy wasn't a big complainer."

San Francisco police officers responded to calls about the shooting at 8:55 a.m. and found one suspect armed with an assault pistol, according to Chaplin. Officers found wounded victims inside the building and brought them out to safety. When officers located the gunman, they said, he put the weapon to his head and shot himself.

"He saw police and turned the gun on himself," Chaplin said. The shooting is not related to terrorism, he added.

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"The company is saddened and deeply concerned about affected employees, family members and the community we share," Gaut said. "Our thoughts and prayers are with all those touched by this incident."

Employees walking outside the facility after the shooting said they did not want to comment on the incident, but some referred to one of the victims as "Big Mike, a "lovely man" who gave others advice and was planning to retire soon.[[428473853, C]]



Witnesses reported that Lam did not say much before he walked in and started firing. He was reportedly still alive when he was taken to San Francisco General Hospital, where he eventually died. Two of the three deceased victims died at the scene of the shooting. Five additional employees suffered various other injuries.



The shooting led to a massive police response and a shelter-in-place warning in an industrial part of the city's Portero Hill neighborhood and surrounding area. UPS described the facility at 2222 17th Street as a package sorting hub and delivery center that employs 850 people.



At the scene, law enforcement officers seized two guns, including a Mac 10-style machine pistol, and a backpack filled with ammunition and three magazines, sources said. NBC Bay Area has also learned that at least one of the guns found at the scene was unregistered.

UPS employees described a scene of chaos and panic as shots rang out right after a morning meeting at the facility.

“They were all in rapid succession,” Raymond Deng, a 30-year-old tech worker who lives across the street from the warehouse, said of the gunshots. “It was like tat, tat, tat, tat, tat, tat, tat.”

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Police activity was first reported near 17th Street and Potrero Avenue, according to a tweet from the San Francisco Police Department at 9:06 a.m.

Tweets from San Francisco residents appeared to show several UPS employees on the roof of the facility with their hands up. Members of the San Francisco SWAT team could be seen going inside the facility and on the rooftop conducting a search.

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According to video from NBC Bay Area's SkyRanger, dozens of UPS employees, some of them in brown UPS uniforms, could be seen exiting the facility single-file, surrounded by police.[[428480603,C]]

UPS driver Marvin Calderon, who witnessed the shooting, told NBC Bay Area the gunman was a fellow employee. Calderon said employees had just finsihed with a daily briefing meeting at 8:50 a.m. "And I jut heard bam, bam, bam, six shots, probably seven, everybody ran out outside on the corner of San Bruno and 17th. And then I heard five more shots."

Calderon said he didn't know the gunman personally. “I just started running out like crazy, like I’ve never run before,” Calderon said."I'm just walking around, trying to clear my mind."



Auto shop owner Robert Kim said he saw “a mob of UPS drivers” running down the street screaming “shooter, shooter.”

Evacuees gathered below the awning of the Il Pirata bar between Potrero Avenue and Utah Street before being escorted to safety.[[428457683, C]]

A witness told NBC News she was driving up Bryant Street with her husband when she saw dozens of UPS employees running in the opposite direction.

Sarah Meier-Heredia said she at first thought it was some sort of “group activity.” But the closer she got to the UPS facility, she saw employees running “haphazardly” in all different directions with a look of “panic on their faces.”

“When we were immediately outside the facility entrance, I saw a tall man that looked to be directing people out and away from the building,” she said. “As the final people came running out, I heard multiple gun shots. At first I thought eight or nine, but maybe more like five or six. Rapid succession, bam bam bam bam bam bam.” She said she ducked in the car while her husband drove off quickly. [[428459733, C]]

Mayor Ed Lee said police saved lives with a “very proactive response.”

“It could have been worse,” he said. “Lives were saved today.”

SFPD tweeted at 10:32 a.m. that they had "contained the building and it was secure." Special Ops continued to search the building for additional victims and witnesses through the afternoon. Muni and traffic routes in the area were rerouted, impacting those on the way to work and school.

The shooting took place the same day a gunman opened fire on Republican lawmakers at a congressional baseball practice in Virginia, injuring House Majority Whip Steven Scalise and four others. The gunman died in the shooting.

A Family Assistance Center is open at 100 Kansas Street for those who need assistance related to the shooting. The Red Cross is also providing services and support.



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NBC News's Andrew Blankstein and the Associated Press contributed to this report.

