San Francisco General Hospital says it has three patients from the shooting, one of whom is in critical condition.
San Bruno Police chief Ed Barberini confirmed that they believe the deceased woman is the suspect in the incident.
He told reporters that “there is no information to suggest” that there is another shooter but that police are “clearing the building in a slow methodical fashion”.
Police said that there is still “an active investigation” at the scene.
The base is located in the San Bruno area outside of San Francisco with police saying that the building has been evacuated.
“We’re trying to do this as orderly as we can but it is pretty hectic,” Barberini said, adding that several hundred have been brought outside.
Police were alerted to the shooting at about 1pm local-time (9pm Irish time).
Youtube workerVadim Lavrusik tweeted that there was an “active shooter at Youtube HQ” and that he heard the sound of shots.He later tweeted that he was safely evacuated.
Youtube’s parent company Google has said that it is advising “employees in the Bay Area, and people with meetings scheduled, to stay away from the area”.
San Bruno city manager Connie Jackson said there had been multiple 911 calls reporting a shooting and that police and fire officials have responded.
TV helicopter video showed officers patting down people grouped outside a building and police vehicles surrounding the area.
Oneeyewitness told CBS News that he saw at least one woman injured and he tried to help her.
“Well I saw the victim and she was in the dining room, and she had a leg injury, a gunshot wound. So I put like a tourniquet on her to try and help her. Then the ambulance came and took her away and put a real tourniquet on her,” the eyewitness said.
He added that he said that she told him she had been shot while in the car park.
Another eyewitness told MSNBC that he saw at least two women with gunshot wounds.
He confirmed that he saw one women being attended to by a member of the public.
“Another lady got shot inside the courtyard, she was on the other side of the tables lying on the ground. But that person got shot ten times, non-stop,” he described.
Read more news of Dublin on our site.