YouTube shooter visited gun range before attack: Police

The 39-year-old Nasim Najafi Aghdam, a Californian resident of Iranian descent, opened fire in a courtyard at YouTube's offices in San Bruno on Tuesday

The woman who opened fire at YouTube headquarters in California over the video sharing platform's "discriminatory" treatment to her postings, practiced shooting at a gun range hours before the attack, police said.

The 39-year-old Nasim Najafi Aghdam, a Californian resident of Iranian descent, opened fire in a courtyard at YouTube's offices in San Bruno on Tuesday.

After practicing, Aghdam then took her 9 mm Smith & Wesson handgun to the Silicon Valley campus and shot three people she apparently did not know, CNN quoted San Bruno Police Chief Ed Barberini as saying on Wednesday.

"We know she was upset with YouTube, and now we've determined that was the motive," Barberini said.

Aghdam shot and wounded three people before killing herself. Two of her victims have been released from the hospital, and one remains in serious condition.

The police were now investigating a website that appears to show the same woman accusing YouTube of restricting her videos, CNN reported. 

The website, which lists four YouTube channels: one in Farsi, one in Turkish, one in English and one devoted to hand art. It also lists an Instagram page that focuses on vegan life.

Her personal website included graphic photos of slaughtered animals and pleas not to wear fur jackets or have sex outside of marriage. She also focused on what she perceived as "discrimination" by YouTube and Google.

A statement from YouTube on Wednesday said the company would increase security at all its offices. Security protections already in place prevented the shooter from entering the building from the courtyard.

It said employees could take time off from work or work from home if they want.

More than 1,100 people work at the YouTube campus in San Bruno, south of San Francisco. 

Employees there include engineers for the site and sales teams that work with advertisers and content creators.