Four people are being treated for gunshot injuries after a shooting at YouTube headquarters in Northern California, police say.
San Bruno Police Chief Ed Barberini said a woman believed to be the shooter was found dead in the building with a "self-inflicted wound".
The condition of the injured, who have been taken to hospital, is unknown.
Earlier, panicked YouTube employees fled the building, in San Mateo county, south of San Francisco.
San Francisco General Hospital is treating three patients from the shooting, and one is in a critical condition, the Associated Press reports.
One employee at a nearby fast food restaurant told Fox station KTVU he had treated a young woman who suffered a gunshot wound to the leg. He said he had fashioned a makeshift tourniquet from a bungee cord as they waited for first responders.
Some 1,700 people work at the YouTube HQ.
Images broadcast on local TV stations showed employees leaving with their hands raised. Other footage appeared to show evacuees forming a queue before being individually frisked by police.
Video captured by a nearby helicopter showed a glass door shattered in its centre, with glass fragments strewn across the ground outside.
Mr Barberini said police arrived at the scene at 12:48 (19:48 GMT) local time after receiving many 911 calls reporting gunshots.
He said officers were faced with "numerous employees fleeing". One victim with a gunshot wound was found at the front of the company headquarters, he said.
YouTube product manager Todd Sherman earlier tweeted that people fled the building in panic.
Another employee, Vadim Lavrusik, initially tweeted he was barricaded in a room with other staff. He later said he had been evacuated.
California Senator Dianne Feinstein tweeted that she was praying for the safety of those at the scene.