A Common Trait Among Mass Killers: Hatred Toward Women

And Scott P. Beierle, who last year shot two women to death in a yoga studio in Tallahassee, had also expressed sympathy with Mr. Rodger in online videos in which he railed against women and minorities and told stories of romantic rejection. Mr. Beierle had twice been charged with battery after women accused him of groping them.

Federal law enforcement officials said the F.B.I. was looking at whether the gunman in Dayton had connections with incel groups, and considered incels a threat.

Experts say the same patterns that lead to the radicalization of white supremacists and other terrorists can apply to misogynists who turn to mass violence: a lonely, troubled individual who finds a community of like-minded individuals online, and an outlet for their anger.

“They’re angry and they’re suicidal and they’ve had traumatic childhoods and these hard lives, and they get to a point and they find something or someone to blame,” said Jillian Peterson, a psychologist and a founder of the Violence Project, a research organization that studies mass shootings. “For some people, that is women, and we are seeing that kind of take off.”

David Futrelle, a journalist who for years has tracked incel websites and other misogynistic online subcultures on a blog called “We Hunted the Mammoth,” described incel websites as a kind of echo chamber of despair, where anyone who says anything remotely hopeful quickly gets ostracized.

“You get a bunch of these guys who are just very angry and bitter, and feel helpless and in some cases suicidal, and that’s just absolutely a combination that’s going to produce more shooters in the future,” Mr. Futrelle said.

Psychiatrists, however, say that the attention on mental health generated by mass shootings, and the common argument that mental illness is the explanation for these massacres, cannot explain the link between misogyny and mass shootings. Misogyny — or other types of hatred — is not necessarily a diagnosable mental illness.

Instead, said Amy Barnhorst, the vice chair of community psychiatry at the University of California, Davis, who has studied mass shootings, what ties together many of the perpetrators is “this entitlement, this envy of others, this feeling that they deserve something that the world is not giving them. And they are angry at others that they see are getting it.”