Four people are dead after a man believed to be an employee opened fire at a San Francisco parcel sorting facility, including the gunman.
After firing on workers, the man turned a gun on himself when confronted by police and died later at a nearby hospital, according to local media.
San Francisco police said the United Parcel Service (UPS) building was secure but offered no immediate information on victims.
Live video showed a massive police presence near the facility, which employs 350, with workers being led out and embracing each other on the sidewalk outside.
"The company is saddened and deeply concerned about affected employees, family members and the community we share. Our thoughts and prayers are with all those touched by this incident," United Parcel Service said in a statement.
Victims were taken to the Priscilla Chan and Mark Zuckerberg San Francisco General Hospital, spokesman Brent Andrew said. He said he could not say how many patients were taken to the hospital or give their conditions.