(Adds lockdown, other details throughout)
SAN FRANCISCO, June 14 (Reuters) - A UPS driver armed with a handgun opened fire at a United Parcel Service Inc package-sorting center in San Francisco on Wednesday, killing three people before fatally shooting himself as officers closed in.
The victims, like the gunman, were also company drivers, said Steve Gaut, head of investor relations at UPS. The man opened fire while the workers were gathered for their daily morning meeting before they were due to head out on their delivery routes, he added.
Two other people were taken to an area hospital with gunshot wounds, San Francisco police said. Authorities did not immediately identify the gunman or the victims.
Police offered no explanation as to a possible motive for the shooting. But Assistant Police Chief Toney Chaplin told a news conference the shooting was not an act of terrorism.
Police recovered two firearms from the UPS facility, including the murder weapon, which they described as an "assault pistol."
The UPS facility, which employs about 350 workers in the city's Potrero Hill area, was initially placed under a security lockdown as a precaution.
The gun violence there erupted hours after another, unrelated mass shooting at a charity baseball practice in the suburbs of the nation's capital left a congressman and several others wounded before the assailant was killed by police.
"We are always saddened by the loss of life to gun violence. Any shooting is one shooting too many," San Francisco Mayor Ed Lee said on Twitter.
Gaut said the facilitys employees were dismissed from work once the lockdown was lifted and that most had since left the building. The company is providing trauma and grief counseling.
Video footage from the scene showed a massive police presence near the facility, with workers being escorted outside and embracing one another on the sidewalk.
"Our thoughts and prayers are with all those touched by this incident," UPS said in a statement. A similar statement of condolence was issued by James Hoffa, president of the Teamsters union that represents UPS workers.
The San Francisco bloodshed came three years after a UPS employee shot and killed two of his supervisors before turning the gun on himself at a UPS distribution center in Birmingham, Alabama. That gunman had recently been fired from the facility.
The deadliest mass shooting in modern U.S. history occurred in June 2016 when a gunman claiming allegiance to the Islamic State militant group killed 49 people at the Pulse nightclub in Orlando, Florida.
Gun laws in the United States rank among the most permissive of any developed country, with the right to "keep and bear arms" enshrined in the Constitution's Second Amendment. Efforts to tighten national gun control measures failed after mass shootings at an elementary school in Newtown, Connecticut, in 2012 and the nightclub shooting in Orlando.
(Additional reporting by Alex Dobuzinskis in Los Angeles, Patrick Enright in Seattle and Nick Carey in Detroit; Writing by Jon Herskovitz and Steve Gorman; Editing by Lisa Shumaker)