Police in San Bruno, Calif., say one person is dead and four people are in hospital after a shooting at YouTube headquarters.

Police believe the person who died — a woman — was the shooter, but they are still investigating, San Bruno Police Chief Ed Barberini said.

"This is an active event and an active investigation," he said. Law enforcement are still searching the business to make sure it's clear.

The chief said that four people were taken to hospital with gunshot-related injuries, but a statement released by the department later clarified that while four people were transported, only three of them had gunshot-related wounds.

"The extent of the victims' injuries are unknown at this time," the statement said.

Tuesday evening, a law enforcement official told the Associated Press the suspected shooter was Nasim Aghdam of Southern California. Multiple U.S. news agencies also named Aghdam as the suspected shooter. 

At a news conference held later Tuesday, the chief confirmed that the fourth injury was someone who had been hurt as they tried to flee the building.

He said the building is now "completely secure" and there's no threat to public safety. The onus now, he said, is on investigators who need to determine exactly what happened at the sprawling office of the video giant.

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