"I'm being discriminated and filtered on YouTube and I'm not the only one," Nasim Aghdam, 39, said in several videos she'd posted.
She also had a website with several complaints about YouTube -- including that it was age-restricting her videos and limiting the number of views they received.
"Videos of targeted users are filtered & merely relegated, so that people can hardly see their videos!" she wrote, adding that celebrities such as Miley Cyrus weren't treated as harshly as she was.
Aghdam took her own life after opening fire in a courtyard of the site's headquarters in San Bruno, authorities said.
Her boyfriend and two other gunshot victims were hospitalized, San Bruno Police Chief Barberini told reporters, adding that a fourth was injured while fleeing.
The boyfriend was reported in critical condition.
"Heard shots and saw people running while at my desk," employee Vadim Lavrusik tweeted from the company headquarters in San Bruno, about 12 miles south of San Francisco. "Now barricaded inside a room with coworkers."
"Safe. Got evacuated it. Outside now," he tweeted a short time later.
"I looked down and saw blood drips on the floor and stairs," tweeted YouTube producer Todd Sherman. “[Peeked] around for threats and then we headed downstairs and out the front."
Video showed people holding their hands over their heads as they fled the complex. Police patted them down, then directed them to a parking lot.
The shooting broke out at the high-tech compound near San Francisco International Airport just before 1 p.m. Pacific time, Barberini said.
Responding officers found one of the victims out front and two others in adjacent businesses, the chief said.
They also found Aghdam's body inside a YouTube building, he said.
Various local, county, state and federal law enforcement officers responded, including heavily armed tactical teams.
After tending to the victims and finding the shooter's body, they conducted a complete, methodical search for any barricaded victims or other employees still inside, the police chief said.
Google, YouTube's parent company, said in a statement: "We continue to actively coordinate with local authorities and hospitals. Our Security team has been working closely with authorities to evacuate the buildings and ensure the safety of employees in the area."
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