SAN BRUNO, Calif. —When word spread that the YouTube shooter wasn’t a disgruntled man but a woman, the almost immediate assumption was dead wrong: that she was a spurned lover intent on killing her boyfriend.

The quick explanation, attributed to witnesses and unidentified law enforcement sources, first streamed across the bottom of newscast crawlers and on news sites. They reported that a domestic dispute had driven Nasim Aghdam to sneak into YouTube’s San Bruno headquarters at lunchtime Tuesday and critically wound one man and injure two women before killing herself.

“When I heard that, I literally smacked my hand into my forehead,” said Jaclyn Schildkraut, an expert on mass shootings and an assistant professor of public justice at Oswego State University in New York. “It was like, ‘Oh, it must be domestic violence because she was a woman.’ “

While female shooters in public places are rare, history shows that love is never behind such attacks. Like men, female shooters —including Aghdam —appear to have been motivated by resentment and anger.

The “spurned woman” assumption in Tuesday’s tragedy is an example of enduring sexism and a double standard, Schildkraut said. Of the 14 “mass shootings” committed by women between 1966 and 2016 —only 4 percent of all mass shootings —not one was fueled by a domestic dispute.

In interviews with Aghdam’s family and in numerous videos she posted on YouTube, it became clear late Tuesday that she was furious at YouTube for what she perceived as the censoring of her graphic anti-animal cruelty videos and her pro-vegan stances that had made her a minor social media celebrity in Iran. She apparently didn’t know anyone at YouTube.

Women practicing at a shooting range in Santa Clara this week rolled their eyes at the mistaken motive that she was a lover seeking vengeance.

“It’s a little offensive,” said Ashley Katena, 29, who had come with a female friend to Reed’s Shooting Range in Santa Clara. “That it’s because she’s an emotional female going on a rampage against her spouse.”

So why were the media and public so eager to accept the explanation of a scorned woman?

Although women are more likely to target people they know, including domestic partners and children, they are less likely to use a gun, more often choosing poison or suffocation, according to Schildkraut’s research. And those crimes tend to happen closer to home. Women who commit such shootings at public places are all the more rare and tend to do so at places that are familiar to them —their own workplaces or schools.

The most memorable woman school shooter remains perhaps one of the first: In 1979, 16-year-old Brenda Spencer fired a .22 caliber rifle from her house to the schoolyard across the street in San Diego, killing the school principal and custodian and wounding a police officer and eight children.

When a San Diego Tribune reporter reached her by phone and asked why she was firing on school children, she uttered a response that would be made into a musical hit by the British band Boomtown Rats: “I don’t like Mondays.”

At the University of Alabama in Huntsville in 2010, biology professor Amy Bishop, who had been denied tenure, opened fire at a department meeting, killing three and wounding three.

“These shooters have similar types of grievances, whether they are perceived or actual, that male shooters do,” said Schildkraut, co-author of “Mass Shootings, Media, Myths and Realities.” “But they are somehow dismissed because of what people believe criminals to be. In our culture today, there is a tendency to justify men’s actions and mitigate or downplay women’s actions in general.”

When 19-year-old Nikolas Cruz killed 17 people at his former Parkland, Fla., high school in February, Schildkraut said, “it was ‘Oh, this poor kid wasn’t loved enough, his mother died, he was an orphan. There were all these justifications of why he did it. The fact is there is no justification.”

The closest to a note or manifesto that Aghdam left to explain her motivations was the angry videos she produced and uploaded to YouTube. She ranted against the company and claimed that YouTube was censoring her videos and cutting into her nascent celebrity and advertising income.

While Aghdam may have shared the kinds of resentments typical of male shooters, she didn’t fit the more common “pseudo commando” persona they tend to take on —the ones who show off caches of weapons on their websites and belts of ammunition slung around their shoulders.

“They’re angry and they plot against people who they believe haven’t given them their due. And in this big display of power, they go out in this perceived blaze of glory to show the world their worth and how powerful they are,” said Amy Barnhorst, a professor and vice chair of community psychiatry at he University of California, Davis. “It’s the narcissist, entitled guy in all that commando gear.”

Aghdam wasn’t that.

While witnesses said she called out something like “come and get me,” from the outdoor patio before killing herself, she carried only a single handgun.

And she didn’t overly concern Mountain View police, who found her sleeping in a parking lot the night before the shootings. From her license plate they learned that her family had filed a missing person’s report a few days earlier. When they notified the family they had found her, the family said they expressed their concern in a follow-up call to police that she had a grudge against YouTube. But police said the family never mentioned anything about her potential for violence. By the next morning she was practicing shooting at a nearby range and by 12:45 p.m. was firing her 9 mm Smith & Wesson into a crowd of panicked employees.

“I don’t necessarily fault them for it,” Barnhorst said of the Mountain View police. “Young males are at the highest risk of perpetrating violence, and middle-aged women are just not up there on the list.”

Like Aghdam, most mass shooters don’t live to explain their motivations: They are either killed or kill themselves during the rampage.

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Greg Woods, a lecturer in San Jose State’s justice studies department, said, “We might be selling ourselves short by focusing on the masculine versus. feminine interpretation rather than trying to understand the pure evil that was this act.”

Still, there’s no real way to know whether she was trying to cast herself, in a twisted, delusional way, as some kind of vengeful heroine.

“Maybe this is what she wanted all along,” he said, “Maybe she embraced the notion of the feminine heroine and saw herself in the starring role.”