The woman who allegedly opened fire at YouTube’s headquarters in a suburb of San Francisco, injuring three before killing herself, was apparently furious with the video website because it had stopped paying her for her clips.

Police in California named the shooter as Nasim Najafi Aghdam.

Aghdam was “upset with the policies and practices of YouTube”, San Bruno police chief Ed Barberini said at a press conference on Wednesday. “This appears to be the motive for this incident.”

No evidence had been found linking her to any individuals at the company where she allegedly opened fire on Tuesday, he said. Police gave her age as 39 but her brother said she would have turned 38 on Wednesday.

Two of the three shooting victims from the incident were released from the Zuckerberg San Francisco general hospital on Tuesday night. A third, a male in his 30s, is currently in “serious condition”, a hospital spokeswoman said Wednesday morning. A fourth victim had been injured, but not shot, in the incident, police said.

Aghdam had visited a local gun range on Tuesday morning before going to YouTube’s headquarters, Barberini said. A Smith & Wesson 9mm semiautomatic handgun, legally registered to Aghdam, was found at the scene.

The alleged shooter parked at a nearby business and appeared to have entered YouTube’s campus through a parking garage.

Local law enforcement agencies are facing questions about a warning her father gave police before the shooting, including that he was concerned she was headed to YouTube’s headquarters, which is more than 500 miles from San Diego, where she lived.

Police in Mountain View, where Google is headquartered, confirmed that they interviewed Aghdam early in the morning before the shooting, after they found her sleeping in her car.

The department described her as “calm and cooperative”, and said that “at no point during our roughly 20-minute interaction with her did she mention anything about YouTube, if she was upset with them, or that she had planned to harm herself or others.”

While her father told police later that morning that Aghdam was upset with YouTube over her videos, and might have come to the area as a result, he did not “mention anything about potential acts of violence or a possibility of Aghdam lashing out as a result of her issues with her videos,” the department said in a statement.

The Mountain View department had not passed on any information about Aghdam to police in San Bruno, where YouTube’s headquarters is located, before the shooting, the San Bruno police chief said.

Aghdam’s online profile shows she was a vegan activist who ran a website called NasimeSabz.com, meaning “Green Breeze” in Persian, where she posted about Persian culture and veganism, as well as long passages critical of YouTube.

Her father, Ismail Aghdam, told the Bay Area News Group from his San Diego home on Tuesday that she was angry with the Google-owned site because it had stopped paying her for videos she posted on the platform, and that he had warned the police that she might be going to the company’s headquarters.

Ismail Aghdam said he reported his daughter missing on Monday after she did not answer her phone for two days. He said the family received a call from Mountain View police at about 2am on Tuesday saying they had found her sleeping in a car.

He said he warned them she might be heading to YouTube because she “hated” the company.

In a statement, the Mountain View police department said officers had found Aghdam asleep in her car around 2am on Tuesday morning, and that they had asked her a series of questions, including “if she was a danger to herself or others.”

Agdham told the officers that she was currently living out of her vehicle while she was looking for the job, a common occurrence in the Bay Area, which has struggled with a homelessness crisis that has left even working families with jobs living out of cars and RVs in quiet areas of Mountain View and Palo Alto.

Aghdam had been reported missing on 21 March, the San Bruno police chief said.

Questions about whether a better law enforcement response to tips might have preventing an attack have emerged repeatedly in the wake of high-profile gun attacks.

The Federal Bureau of Investigation admitted that it failed to properly follow up on two separate tips that the gunman in the Parkland, Florida, massacre in February was planning on attacking a school, including a call from a person close to suspect Nikolas Cruz, who noted that he was armed.

The incident also raised questions about security measures at Sillicon Valley’s lavish tech campuses. Law enforcement officials are “always looking for opportunities to harden targets or making environments as safe as possible for people who work there”, Barberini said.

A female shooter is a rarity: an FBI study of 160 “active shooter” incidents between 2000 and 2013 found only six incidents, or 3.8%, were perpetrated by a female shooter. Five of those six shootings were incidents of workplace violence, where women attacked current or former co-workers at the places they had worked. All of these female shooters used handguns.

One recent mass shooting, the 2014 San Bernardino attack, had a joint male and female perpetrator. Married couple Syed Farook and Tashfeen Malik opened fire on a holiday party of Farook’s co-workers in 2014 with military-style rifles, leaving 14 people dead.

Aghdam’s social media posts highlighted pro-vegan views and criticised animal cruelty. She was also 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. “For me, animal rights equal human rights,” Aghdam told the Union-Tribune at the time.

Many video creators on YouTube have spoken publicly in recent months about their frustrations with YouTube’s new restrictions on which videos can earn ad revenue, a change that many said hurt smaller video producers.

YouTube’s policy changes were announced following corporate outrage last year when an investigation found that ads for mainstream brands were being shown on YouTube videos advocating racist and extremist views. But video creators have said that YouTube’s response to this problem, including having some channels “demonetized”, ended up hurting small, independent video producers who tackled serious topics, not just videos propagating extremist content.

“She was always complaining that YouTube ruined her life,” Nasim’s brother, Shahran Aghdam, told the Bay Area News Group on Tuesday night.

YouTube terminated Aghdam’s account following the shooting. Her Instagram and Facebook accounts have also been removed.

A screenshot of a video posted on Aghnam’s YouTube channel before it was taken down showed her complaining that “YouTube filtered my channels to keep them from getting views”.

Associated Press and Reuters contributed to this report