WASHINGTON — In the spring of 2016, Brian Levin found himself in an uncomfortable position: trying to save the life of a Ku Klux Klan member.

Levin, a former New York City cop who studies domestic extremism as the director of the Center for the Study of Hate and Extremism at California State University, was documenting a Klan rally in Anaheim, California, when a counterprotest suddenly took a violent swing — forcing Levin to physically place himself between a Klansman and a furious, anti-fascist mob that seemed ready to kill.

It made Levin wonder if in his focus on the obvious subject — the white supremacists — he’d overlooked a growing source of extremism: the far left. “At that point, I said we have something coalescing on the hard left,” Levin told VICE News.

Wednesday morning’s shooting of Republican lawmakers at a baseball practice in Virginia seemed to raise the question again. The shooter, James T. Hodgkinson, was a Bernie Sanders-supporting man from Illinois with a record of anti-Trump rantings on social media. His politics have quickly become a talking point among some conservative pundits seeking a quick political score: proof of a looming leftist campaign against the government.

Experts in homegrown extremism say it’s not so simple — Hodgkinson had no known association to any left-wing extremist group. But they also say that the past few months have seen enough of a rise in politically motivated violence from the far left that monitors of right-wing extremism have begun shifting their focus, and sounding the alarm. They see indications that the uptick in extremist rhetoric and anti-government activism that characterized the early years of the Obama presidency are beginning to manifest on the far left in the early days of Trump’s, and that the two sides are increasingly headed for confrontation.

“I think we’re in a time when we can’t ignore the extremism from the Left,” said Oren Segal, the director of the Center on Extremism, an arm of the Anti-Defamation League. Over the past few months, the ADL, which hosts regular seminars on homegrown extremism for law enforcement officials, has begun warning of the rising threat posed by far-left groups, most recently at a seminar just this past Sunday. “When we have anti-fascist counterprotests — not that they are the same as white supremacists — that can ratchet up the violence at these events, and it means we can see people who are violent on their own be attracted to that,” Segal said. “I hate to say it, but it feels inevitable.”

The evidence is so far largely anecdotal. Levin says that since December 2015, he’s documented nearly two-dozen episodes in California where political events turned violent because of agitation on both sides, something he says he hardly ever saw before. Now, there are violent clashes on college campuses involving groups like Antifa, the anti-fascist group, taking on the alt-right; and aggressive anti-Trump rallies attended by members of the Redneck Revolt, a new pro-minority, anti-supremacist group that encourages its members to train with rifles. Online, hard leftists increasingly discuss politics in dire terms, and rationalize violence as a necessity— even the true inheritor of traditional progressive activism. (Or, in the case of the “Punch a Nazi” meme, a fun game.)

Left-wing extremism, of course, is nothing new. Groups like the Weather Underground and the Black Panthers have deep roots, and in the years after 9/11, Segal says, the largest source of extremist violence was from the Left: eco-terrorists and animal rights activists. But those later organizations mostly targeted institutions; in the modern era, politically motivated violence perpetrated by angry lone-wolf attackers bearing automatic rifles, of the sort carried out in Wednesday’s attack, has until now largely been a modus operandi of the far right.

In a recent interview with VICE News Tonight, a chapter leader of one newly formed anti-fascist group called Redneck Revolt said the group has taken up guns only in self-defense. “We are a response to a rise in politically motivated violence and intimidation against vulnerable communities,” said the chapter leader, who asked to be identified only by a first name, Mitch. “That doesn’t mean that we’re, like, looking for a fight. We’re just trying to defend ourselves.”

Redneck Revolt doesn’t self-identify as “left,” but its ideals tend to fall along the liberal side of the spectrum: pro-Muslim, pro-immigrant, pro-LGBT, anti–economic inequality. But Mitch said that as the group has reached out to other organizations, like the local Three Percenter Militia, a largely right-wing, anti-Obama group, they found unlikely sources of commonality, particularly in their focus on local sovereignty, and general concerns about the direction of the country. Some former members of Three Percenters have even become involved in their activities — after “extensive vetting,” Mitch said.

Chris Hamilton, an expert on American extremist movements at Washburn University in Topeka, Kansas, says anti-authoritarian sentiment may be blurring what once seemed to be clear ideological lines. “If you think about it, leftists never joined the National Rifle Association — unless they were radicals, they never thought about stockpiling weapons,” he said. “Ok. Well, maybe we’re entering a period where leftists will start thinking about things in that way, like the eco-radicals did in the ’70s.”

Hamilton says that as he browses far-left websites and listens to left-wing talk radio, he hears some of the same sentiments he’s been hearing for years on the right. “These days, that kind of sentiment is popping up in the middle and on the left; it’s not just in the sovereign citizen movement,” he said. “I’m really worried about rising civil strife in the U.S.”

Levin is worried about it too: The embrace by the far left of tactics that were previously the purview of the far right means the level of political tension in the country can only go up. “I’ve been going up and down the state of California meeting with law enforcement officials about this. I’m very concerned about it,” he said. “What we’re seeing is the democratization of extremism and the tactics of radicalism. I’ve been warning about this, and nobody gave a shit.”

Watch the VICE News Tonight report on leftist extremism: