Nasim Aghdam, 39, of Southern California, was identified by US media citing police officials as the woman who approached the campus around lunchtime and began to fire before entering the building of the Google-owned video sharing service.
One man and two women were shot in the incident before the female shooter apparently committed suicide.
Law enforcement officials identified the suspect to multiple media outlets and said the shooting was being investigated as a domestic dispute.
Police have yet to officially the name the suspect.
YouTube shooting suspect Nasim Aghdam, who describes herself as a vegan artist, bodybuilder, and animal rights activist, often lashed out at the video platform for censoring and demonetizing her content pic.twitter.com/AsQiCz3SHB— Brianna Sacks (@bri_sacks) 4 avril 2018
Aghdam had a significant internet presence before her clips were scrubbed and her account deleted in the aftermath of the shooting.
She reportedly posted videos under the name “Nasim Wonder1,” with some dating back to 2011.
According to NBC, she says in a video posted in January 2017 that YouTube “discriminated and filtered” her content. In the video, Aghdam reportedly says her channel used to get lots of views but that after being “filtered” by the company, it received far fewer views.
She complained YouTube had imposed an age restriction on one of her workout videos because it was too racy, yet it hadn't taken the same action for stars like Miley Cyrus and Nicki Minaj, whose videos, she said, were inappropriate for children.
On the website NasimeSabz.com, identified as hers by the San Francisco Chronicle, she had several posts about Persian culture and veganism, interspersed with rants against YouTube.
Those complaints included claims the company was not sharing enough revenue with people who create videos for the platform.
"There is no free speech in real world and you will be suppressed for telling the truth that is not supported by the system," she wrote in one post.
"There is no equal growth opportunity on YouTube or any other video sharing site."
In an Instagram post dated March 18, Aghdam complains again about YouTube's alleged censorship, saying it was using its tools to “censor and suppress people who speak the truth and are not good for the financial, political gains of the system and big businesses.”
Her most recent YouTube video came three weeks ago and was titled “Leg Exercises At Home Fitness.”
Aghdam was also a prominent animal rights protester.
She was quoted in a 2009 story in the San Diego Union-Tribune about a protest by People for the Ethical Treatment of Animals against the use of pigs in military trauma training.
She dressed in a wig and jeans with drops of painted "blood" on them, holding a plastic sword at the demonstration outside the Camp Pendleton Marine Corps base.
"For me, animal rights equal human rights," Aghdam told the Union-Tribune at the time.
A message on her YouTube accounts said the pages were removed due to “multiple or severe violations of YouTube’s policy against spam, deceptive practices, and misleading content or other Term of Service violations.”