Google and YouTube's most senior staff have responded to the shooting at the video site's headquarters that left at least one person dead.
YouTube staff were sent fleeing for cover after a woman entered its headquarters with a handgun and injured at least three people, before taking her own life. Her motives still remain unclear, but police have said she appeared to hold a grudge against the company.
The bosses of both Google and YouTube have spoken out about the shooting, describing the company as a "family" and thanking law enforcement for their response to the attack.
"There are no words to describe how horrible it was to have an active shooter @YouTube today," wrote Susan Wojcicki, YouTube's CEO. "Our deepest gratitude to law enforcement & first responders for their rapid response. Our hearts go out to all those injured & impacted today. We will come together to heal as a family."
Google boss Sundar Pichai echoed her sentiment in a tweet posted on his personal account.
"There are no words to describe the tragedy that occurred today," he wrote. "@SusanWojcicki & I are focused on supporting our employees & the @YouTube community through this difficult time together. Thank you to the police & first responders for their efforts, and to all for msgs of support."
Mr Pichai also sent a much longer note to all Google employees.
The shooting began when a woman approached an outdoor patio and dining courtyard on the campus around lunchtime and began to fire before entering the building, police said.
The San Jose Mercury News, citing a law enforcement source, said that she was targeting her boyfriend due to a domestic dispute.
A U.S. government security official told Reuters there was no known connection to terrorism.
ABC News, citing unnamed law enforcement sources, said the suspect was 35 to 40 years old, and lived in Southern California, with no apparent connection to YouTube.
A YouTube product manager, Todd Sherman, described on Twitter hearing people running, first thinking it was an earthquake before he was told that a person had a gun.
"At that point every new person I saw was a potential shooter. Someone else said that the person shot out the back doors and then shot themselves," Sherman said in a tweet.
"I looked down and saw blood drips on the floor and stairs. Peaked around for threats and then we headed downstairs and out the front," Sherman said.
The shooting was the latest in a string of mass killings carried out in the United States in recent years. Most recently, the massacre of 17 people at a Florida high school has led to calls for tighter restrictions on gun ownership.
In a recording of a 911 call posted online by the Los Angeles Times, a dispatcher can be heard saying: "Shooter. Another party said they spotted someone with a gun. Suspect came from the back patio ... Again we have a report of a subject with a gun. They heard seven or eight shots being fired."
Dozens of emergency vehicles quickly converged on the YouTube campus, and police could be seen on televised aerial video systematically frisking several employees leaving the area with their hands raised.
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 the victims.
The three patients taken to San Francisco General Hospital were all awake, Dr. Andre Campbell, a trauma surgeon at the hospital, said at a news conference. All three people were victims of gunshot wounds, Campbell said, but none of them had undergone surgery. A fourth person was taken to a local hospital with an ankle injury from fleeing the scene.
In response, Twitter Chief Executive Jack Dorsey tweeted: "We can't keep being reactive to this, thinking and praying it wonât happen again at our schools, jobs, or our community spots. Itâs beyond time to evolve our policies."
Last month, YouTube announced it would ban content promoting the sale of guns and gun accessories as well as videos that teach how to make guns.
Female mass shooters are rare. A recent Washington Post analysis shows only three out of 150 U.S. shootings with more than four victims since 1966 were done by women. In 2015, a husband and wife killed 14 people in San Bernardino, California.
Additional reporting by agencies
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies