SAN BRUNO, Calif. — Law enforcement officials have identified the suspect who opened fire Tuesday at YouTube Headquarters in California.
Police say 39-year-old Nasim Najafi Aghdam opened fire with a handgun in an outdoor courtyard before killing herself.
Investigators say the suspect did not know the three victims she shot.
A 36-year-old man was in critical condition, a 32-year-old woman was in serious condition and a 27-year-old woman was in fair condition, a spokesman for San Francisco General Hospital said.
Sources say the suspect had a long-running dispute with YouTube.
The suspect's father says she was angry at the company because it stopped paying her for videos she posted.
He reported her missing on Monday, and warned police that his daughter might be going to YouTube.
After receiving multiple 911 calls reporting gunfire, officers and federal agents swarmed the company's suburban campus sandwiched between two interstates in the San Francisco Bay Area city of San Bruno, as terrified employees huddled inside.
YouTube employee Dianna Arnspiger said she was on the building's second floor when she heard gunshots, ran to a window, and saw the shooter on a patio outside.
She said the woman wore glasses and a scarf and was using a "big huge pistol."
"It was a woman and she was firing her gun. And I just said, 'Shooter,' and everybody started running," Arnspiger said.
She and others hid in a conference room for an hour while another employee repeatedly called 911 for updates.
"It was terrifying," she said.
The NYPD said it was closely monitoring the situation.
NYPD Counterterrorism officers were seen on patrol outside Google's offices in Chelsea on Tuesday night. Google owns YouTube.
NYPD Counterterrorism officials said there is no known threat to New York City, but their officers were posted outside YouTube and Google offices Tuesday night for precautionary reasons.
The White House said President Donald Trump was briefed on the shooting and that officials were monitoring it.
Television news footage showed people leaving the building in a line, holding their arms in the air for police to inspect as they were leaving the building. Officers patted down people to make sure none had weapons, and police vehicles surrounded the area.
Officers discovered one wounded victim when they arrived and then found the shooter with what appeared to be a self-inflicted gunshot wound several minutes later, San Bruno Police Chief Ed Barberini said.
He said two additional gunshot victims were found minutes later at an adjacent business. Barberini initially said there were four shooting victims but later clarified that a fourth person suffered an ankle injury.
The headquarters has more than a thousand engineers and other employees in several buildings. Originally built in the late 1990s for the clothing retailer Gap, the campus south of San Francisco is known for its sloped green roof of native grasses.
Inside, Google, which owns the world's biggest online video website, famously outfitted the office several years ago with a three-lane red slide for workers to zoom from one story to another.
Zach Vorhies, 37, a senior software engineer at YouTube, said he was at his desk working on the second floor of one of the buildings when the fire alarm went off. He got on his skateboard and approached a courtyard, where he saw the shooter yelling, "'Come at me, or come get me.'"
There was somebody lying nearby on his back with a red stain on his stomach that appeared to be from a bullet wound.
He said he realized there was an active shooter when a police officer with an assault rifle came through a security door. He jumped on his skateboard and took off.
Google said the company's security team worked with authorities to evacuate buildings and was doing whatever it could support the victims and their families. The Bureau of Alcohol, Tobacco, Firearms and Explosives said it also responded.
"Today it feels like the entire community of YouTube, all of the employees, were victims of this crime," said Chris Dale, a YouTube spokesman. "Our hearts go out to all those who suffered."
Will Hudson said a friend who works for YouTube texted him about the shooter.
"I think there might be a shooter in my building," read one text. "The fire alarm went off so we started to evacuate and then people (started) running saying there was a shooter."
Hudson said his friend made it safely back to San Francisco and was in contact with his family. Hudson said he's become used to hearing about gun violence but has never been so close to it before.
"It just feels strange. It feels like it could really be anyone. That's really the strangeness of it," he said.
Google CEO Sundar Pichai called the shooting at the YouTube headquarters "a horrific act of violence.''
He said the parent company of YouTube is doing everything it can to support the victims and their families.
Pichai also said the company "will continue to provide support to help everyone in our Google family heal from this unimaginable tragedy.''
Associated Press writers Michael Balsamo in Los Angeles, Eric Tucker in Washington and Janie Har in San Francisco contributed to this report.
This story has been corrected with new information from authorities that three victims suffered gunshot wounds and a fourth was taken to the hospital but wasn't shot. A reference also has been removed to patients being taken to Stanford Hospital because the facility says it gave incorrect information.