Another witness told KRON4's Gabe Slate a woman who was shot at the headquarters crawled into the Carl's Jr. next door.
It is unknown if the woman shot herself or was shot by someone else, such as law enforcement.
A witness tells KTVU the shooting was very fast and there was gunfire both inside and outside of the building.
Police say the shooter is dead from a self-inflicted gunshot wound.
One victim was found with an apparent gunshot wound in front of the building.
Police in Northern California say they're responding to an active shooter at YouTube headquarters.
City Manager Connie Jackson says there have been multiple 911 calls reporting a shooting and that police and fire officials have responded.
Yankees set for first home game despite snow
Stroman, limited to two starts in spring training because of a sore shoulder, walked three and struck out eight. It was Toronto's first straight steal of home since Aaron Hill did it against NY on May 29, 2007.
While the scene is considered clear and the threat is over, Barberini said the investigation continues.
He later tweeted that he was safely outside the building.
San Bruno Police tweeted at 1 p.m.to avoid the area due to police activity.
There are also unconfirmed reports that the suspect has shot themselves. Now barricaded inside a room with coworkers.
Google communications tweeted: "Re: YouTube situation, we are coordinating with authorities and will provide official information here from Google and YouTube as it becomes available".
Employees recounted frantic scenes as they fled the headquarters of the Google-owned video sharing service near San Francisco, with one saying he saw blood on the floor as he escaped.
President Trump tweeted his thoughts and prayers for the victims and thanked first responders.
As he headed toward the exit, someone informed him there was a person with a gun.