Father of alleged YouTube shooter apologizes: 'I am sorry. I can't believe it'

"I am sorry. I can't believe it," Ismail Aghdam told ABC station KGO.

"I apologize. All the U.S. people, all the humans, I apologize. I am sorry. I can't believe it," Ismail Aghdam told ABC station KGO outside his home in Riverside County, where authorities spent the day searching the residence, as well as a home in San Diego where his daughter had apparently lived with her grandmother.

Four people were injured in the shooting -- three with gunshot wounds and one with an ankle injury from running from the scene, according to the San Bruno Police Department.

Nasim Aghdam died of an apparently self-inflicted gunshot wound, police said. She legally possessed and owned the handgun that authorities recovered from the scene. It was unclear from where it was purchased.

The motive for Tuesday's shooting was initially unclear, as there was no evidence linking the suspect to anyone at the scene. But police and Nasim Aghdam's family said she was upset with YouTube.

The woman's family told investigators she was a prolific YouTube user who had recently created a series of videos for her channel advocating for veganism and against animal cruelty. But she apparently developed a grudge against the video-sharing site after it changed its filtering policy, causing her to lose followers.

Nasim Aghdam accused YouTube of censoring her content and cutting her advertising revenue.

"I'm being discriminated and filtered on YouTube and I'm not the only one," she said in a video she posted.

When asked if she had a history of mental illness, Nasim Aghdam's family told KGO "no."

The woman's brother told ABC affiliate KGTV he knew his sister "had a problem with YouTube." So when he learned that police in nearby Mountain View had found her asleep in her car Tuesday morning, he became concerned and contacted authorities.

"I Googled 'Mountain View' and it was close to YouTube headquarters, and she had a problem with YouTube," her brother said. "So I called that cop again and told him there’s a reason she went all the way from San Diego to there, so she might do something."

But police said Nasim Aghdam's family did not give them a warning.

"At no point during that conversation did either Aghdam’s father or brother make any statements regarding the woman’s potential threat to, or a possible attack on, the YouTube campus. Also, there was no indication from either Aghdam or her family that she may have been in possession of any weapons," the Mountain View Police Department said in a statement posted on its official Facebook page Wednesday.

In a statement to ABC News on Wednesday afternoon, Nasim Aghdam's father said his family is in "absolute shock" and they feel the "utmost regret" and "sorrow" in the wake of the shooting.

"Our family is in the absolute shock and can’t make sense of what has happened," Ismail Aghdam said. "Although no words can describe our deep pain for this tragedy, our family would like to express their utmost regret, sorrow for what happened to innocent victims. Our thoughts and prayers are with them and their families. We are praying for speedy recovery of the injured and ask God to bestow patience upon all persons hurt in this horrific senseless act."

He added, "As our family struggles to cope with this chaotic situation we would like to kindly ask the media to respect our privacy and we thank the authorities."