A woman opened fire at YouTube's headquarters near San Francisco, sending employees scrambling into the street and at least three victims to local hospitals before taking her own life, police said.
Police in Northern California responded to reports of an "active shooter" at the company's campus in San Bruno, south of San Francisco, at about 12.47pm local time.
Police said a short time ago that at least three victims had been taken to hospital with gunshot wounds, and one woman was found dead inside the building, apparently from a self-inflicted gunshot wound.
Police did not release any further information on the suspect or speculate on her motives for the shooting at the offices of YouTube, which is owned by Google.
"We did locate a victim with what we believe to be a self-inflicted gunshot wound. It's a female," San Bruno Police Chief Ed Barberini said at a news conference, describing the person police believe was the shooter.
One of the victims, a 36-year-old man, was listed in critical condition at San Francisco General Hospital. A 32-year-old woman was listed in serious condition and a 27-year-old woman in fair condition. Authorities did not release names of any of the victims.
Witnesses had described seeing blood on the floor and stairs.
Multiple ambulances are at the scene and authorities have warned the public to stay out of the area.
Local television images showed YouTube employees walking out of the building with their hands raised.
YouTube employee Todd Sherman tweeted that people fled the building in panic.
We were sitting in a meeting and then we heard people running because it was rumbling the floor. First thought was earthquake. https://t.co/gmolQmRXm1— Todd Sherman (@tdd) April 3, 2018
Another employee, Vadim Lavrusik, initially tweeted he was barricaded in a room with other staff. He later said he had been evacuated.
Active shooter at YouTube HQ. Heard shots and saw people running while at my desk. Now barricaded inside a room with coworkers.— Vadim Lavrusik (@Lavrusik) April 3, 2018
Others witnesses also took to Twitter to describe the scene.
Last month, YouTube announced it would ban content promoting the sale of guns and gun accessories as well as videos that taught people how to make guns.