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.