Two law enforcement sources said Aghdam had previous addresses in Riverside and San Diego counties. Neighbors in Menifee said Aghdam lived in a home with her parents.
One neighbor said Aghdam did not really come out of the home much and that the family kept to themselves.
Authorities later confirmed her identity and said Aghdam, 39, was originally from San Diego.
She allegedly also had a website with a manifesto that targeted YouTube for censorship and demonetization of her video content.
Aghdam is said to have no relationship with anyone in the YouTube facility.
Earlier Tuesday, Mountain View police said they found Aghdam asleep in a car in a parking lot. The officers contacted her and found out she was reported as a missing person from Southern California.
Authorities said Aghdam confirmed her identity and answered questions. Her family was notified that she had been found.
Aghdam's brother told ABC7 sister station KGO-TV that he Googled Mountain View, found that it was close to the YouTube headquarters and said he called the department back.
"So I called the cop again and told him she went all the way from San Diego, so she might do something," he said.
Shortly before 1 p.m., Aghdam was suspected of heading to the San Bruno headquarters of YouTube and opening fire.
Three people were injured by gunshot wounds and a fourth suffered an ankle injury.
Sources said Aghdam did not have an ID badge but was carrying a purse. Nobody in the facility knew who she was. They added that Aghdam got off 30 or 40 shots before turning the gun on herself.
According to her website, a possible motivation for the shooting could have been tied to her many YouTube accounts, which she said saw a decline in viewership over the past few months.
San Bruno police said they were still investigating a motive and that there is no evidence that Aghdam knew the victims she shot or that anyone was specifically targeted.
Earlier reports indicated that the shooting may have resulted from a domestic situation, but later pulled back from those statements.
She embedded videos from the biggest YouTubers on the platform on her website, including massive creator Casey Neistat. In them, they talk about the YouTube "Ad-apocalypse" where many users are seeing massive dips in traffic, subscriber count loss and demonetization of videos.
Neistat has more than 9 million subscribers and made a famous video about the YouTube ad revenue scare for creators.
It appeared that Aghdam was disgruntled by the changes in the YouTube platform.
She wrote on her website, "Be aware! Dictatorship exists in all countries but with different tactics! They only care for personal and short-term profits and do anything to reach their goals even by fooling simple-minded people, hiding the truth, manipulating science and everything, putting public mental and physical health at risk, abusing non-human animals, polluting the environment, destroying family values, promoting materialism and sexual degeneration in the name of freedom and turning people into programmed robots!"
She goes on to quote Adolf Hitler saying, "Make the lie big, make it simple, keep saying it and eventually they will believe it."
The rest of her message targets YouTube and censorship.
"There is no free speech in the real world and you will be supressed for telling the truth that is not supported by the system. Videos of targeted users are filtered and merely relegated so that people can hardly see their videos," it said.
On Feb. 20, YouTube enacted a new advertising policy that demonetized channels with less than 1,000 subscribers and 4,000 hours of watch time. Though Aghdam's main English channel had more than 15,000 subscribers, many of her videos appeared to be demonetized.
ABC7 sister station KGO-TV contributed to this report.