Rittenhouse is emerging as the poster boy for that phenomenon. Outraged by the shootings, activists rushed to pin him with various far-right ideologies. Hundreds, probably thousands, of social media posts describe him as a militia member or a white supremacist. Some have referred to him, without evidence, as part of the misogynistic incel movement.
Reporters and researchers across the country are digging into Rittenhouse's background and, so far, they've come up with no clear-cut evidence of ties to antigovernment militias or to the "boogaloo boys," armed men in Hawaiian shirts calling for violent revolution.
Social media accounts linked to Rittenhouse portrayed a police booster aligned with "Back the Blue," pro-cop activism widely seen as a racist response to Black Lives Matter. But as of Friday there was no indication of Rittenhouse's membership or support of groups categorized as traditional hate or extremist groups.
The kind of violence witnessed in Kenosha is straining Americans' vocabulary for what they're seeing. The murkiness of protests and the growing presence of armed activists on the left make it difficult to distinguish who's who among gun-toting people at the scene. Do we call them vigilantes? Counterprotesters? Militias? Violent extremists?
"I think the confusion understandably comes from different groups having similar appearances and some shared goals, especially in a moment like this," said Amy Cooter, a sociologist at Vanderbilt University who's written extensively about militias and related "Patriot Movement" groups.
Take, for example, the widespread linking of Rittenhouse to the far-right militia movement, based on rather slim evidence. Rittenhouse had been seen mingling with apparent members of a group calling itself the Kenosha Guard. Researchers said it's likely an ad hoc formation in response to the protests that erupted this week after police shot Jacob Blake, a Black man, seven times in the back as his children watched.
As in other cities, armed volunteers began organizing in Kenosha, ostensibly to protect local businesses from what they see as out-of-control leftist mobs.
"Any patriots willing to take up arms and defend our city tonight from the evil thugs?" the Kenosha Guard posted Tuesday on Facebook. "No doubt they are currently planning on the next part of the city to burn tonight."
Pitcavage said Facebook took down the Kenosha Guard's page before he and other researchers could study its members or mission in depth. Pitcavage said there is no confirmation that Rittenhouse answered the group's call for volunteers or had ties to that or any other group at the scene.
Facebook has said it has not found a connection between the Kenosha Guard and the shooting, but removed the group because it violated newly introduced policies aimed at militias and other groups tied to violence.
Even the group's "militia" description appears to come from a single mention from an organizer.
"The word 'militia' has several different meanings," Pitcavage said. "It can mean a group within the specific militia movement, but it can also be more generically used for any armed paramilitary group. And some people, although they shouldn't, use it even more loosely for any armed group."
This collapsing of terms is frustrating to extremism analysts who are fastidious about the categories and context of the incidents they study. J.J. MacNab, a researcher who regularly tweets about militia and vigilante cases, was conspicuously silent as debate over Rittenhouse snowballed on social media, hardening into two camps: Those who see a racist domestic terrorist versus those who justify the killings as self-defense.