Authorities in the US have confirmed that the suspect behind the shooting at the YouTube HQ was a 39-year-old woman from San Diego, California "angry" with the organisation after it was de-monetised and removed from the video-sharing website.
Nasim Aghdam, who described herself on her website as a Persian animal rights activist and vegan athlete, opened fire with a handgun at YouTube HQ on Tuesday just before 1pm, Pacific Time.
She had been reported missing by her family earlier that day.
Following the shooting, a 36-year-old man was reported as in critical condition, while a 32-year-old woman was in serious condition and a 27-year-old woman was in fair condition. The three victims are still hospitalised, while a fourth victim was also taken to the hospital with injuries.
Aghdam was found dead by police inside the building as the result of self-inflicted gunshot wounds. Law enforcement officials in California later confirmed her identity.
According to Aghdam's family, she was "angry" that YouTube had stopped paying her for online videos and had taken down her material.
Active shooter at YouTube HQ. Heard shots and saw people running while at my desk. Now barricaded inside a room with coworkers
On her website, Aghdam wrote: "Videos of targeted users are filtered and merely relegated, so that people can hardly see their videos."
"There is no equal growth opportunity on YouTube or any other video-sharing site. Your channel will grow if they want [it] to!"
Aghdam's family had reported her missing after she disappeared from southern California, and she was found sleeping the night before the attack in her car in Mountain View, near the YouTube offices.
Her channel, Nasime Wonder1, which has now been deleted, had about 5,000 subscribers.
At the time of the shooting on Tuesday, San Bruno Police warned people on Twitter to "please stay away from Cherry Ave & Bay Hill Drive" as they are responding to an "active shooter".
A YouTube product manager who goes by the name of Vadim Lavrusik took to Twitter to communicate that he and his co-workers were barricaded inside a room at 901 Cherry Avenue headquarters, before later tweeting: "Safe. Got evacuated. Outside now."
"Active shooter at YouTube HQ. Heard shots and saw people running while at my desk. Now barricaded inside a room with coworkers."
A Google employee at a nearby complex said several police sirens were heard around the office and that colleagues inside the building are texting them updates. Videos and photos posted to Snapchat show police officers running into the YouTube offices.
People were also seen evacuating the offices in a line with their hands up in the air. Television reports also showed police officers patting down people who had left the building to check for weapons.
In a statement, Google said it is "coordinating with authorities" and will provide official information here from Google and YouTube as it becomes available.
An earlier version of this article claimed that Nasim Aghdam was transgender. This was incorrect and we have updated the article accordingly. We apologise for the error and any offence caused.
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