An abiding sense of loyalty to the fringe online conspiracy movement known as QAnon is emerging as a common thread among scores of the men and women from around the country arrested for their participation in the deadly U.S. Capitol insurrection, court records reveal.

The FBI first labeled QAnon and its fluid online community of supporters as a “dangerous extremist group” in August 2019, and over the past two weeks it has featured prominently in criminal indictments filed against many of those alleged to have participated in the Jan. 6 Capitol riot, including a number accused of egregious crimes.

Among them is Douglas Jensen, the bearded man seen in a viral video wearing a distinctive “Q” T-shirt, menacing a lone black U.S. Capitol Police officer as he led rioters through the halls and pushed the mob deeper into the Capitol building. Jensen later told investigators that he “intentionally positioned himself” toward the front of the mob so his T-shirt would be visible to cameras and “Q” could “get the credit,” according to an FBI affidavit.

Cleveland Meredith Jr., who the government also believed to be a supporter of QAnon theories, allegedly posted online about his desire to execute House Speaker Nancy Pelosi by “putting a bullet in her noggin on Live TV,” according to court records. He went to Washington, D.C., armed with multiple firearms and more than 2,500 rounds of ammunition in his possession, according to prosecutors. He was late to the rally because his car broke down.

At least three more individuals charged on Tuesday are believed to be supporters of the QAnon theory, according to new FBI records.

The high profile of QAnon adherents in the Capitol riots represents what experts describe as a stunning evolution from a harmless fringe forum for people peddling outlandish conspiracies to a gathering space for those intent on plotting domestic terror — and the transformation could present a vexing new challenge for law enforcement.

“We don’t have a good predictor of where it’s going to go,” said Mary McCord, a former federal prosecutor and expert in homegrown terror groups who called it “extremely troublesome” to see some elected officials fanning the flames of twisted QAnon theories.

“You actually have elected members of Congress who, at best, are not condemning Q, and at worst are actually espousing some of the crazy conspiracy theories — dangerous conspiracy theories,” McCord said.

Two newly elected members of the House of Representatives pushed QAnon messages ahead of the 2020 elections. And notably, President Donald Trump brushed aside questions about QAnon when pressed about it before the election in October, saying he knew “nothing” about it.

“I do know they are very much against pedophilia, they fight it very hard,” Trump said while refusing to condemn the false theories at an Oct. 15 town hall event.

Just weeks earlier, at a White House press briefing in August, the president said QAnon followers “love the country” and added that he appreciated their support — which in turn helped embolden belief in the movement.

“He said a whole lot by not saying a whole lot at all. For a lot of us supporters, we knew that he really couldn’t come out and say, ‘Oh yes, I support it,” Gina Sink, 55, a QAnon supporter from Lexington, N.C., told ABC News at a Trump rally in September following the president’s comments.

“Following the November 3, 2020 election, many QAnon adherents began pushing false and discredited theories of massive voter fraud and that the 2020 election had been ‘stolen’ from President Trump,” the Department of Justice warned in a new affidavit on Tuesday.

On Jan. 6, the influence of QAnon on rioters was evident in the mountain of social media videos and photos depicting their raid on the Capitol complex. Several rioters were seen wearing “Q” clothing, and chanting slogans tied to the movement. In a Jan. 13 bulletin prepared by the FBI for law enforcement partners, federal agents reported that “symbols associated with QAnon conspiracy theories” were widely displayed by rioters.

In charging documents, federal prosecutors have noted the apparent influence of QAnon among several participants accused of threatening violence during the siege.

Jacob Chansley, the horned helmet-wearing rioter who was one of the most widely recognized from the incident, is also believed to be a supporter of QAnon theories.

“Chansley is an active participant in — and has made himself the most prominent symbol of — a violent insurrection that attempted to overthrow the United States Government on January 6, 2021,” government prosecutors said, using some of its bluntest words yet to describe the riot.

The Jan. 6 attack proved deadly to at least two QAnon adherents. Rosanne Boyland, 34, who was reportedly crushed by the crowd at the Capitol complex, had recently started following QAnon conspiracy theories online, her sister later told the Associated Press. And Ashli Babbitt, who was shot and killed by a U.S. Capitol Police officer inside the Capitol, was later characterized in an FBI bulletin as “an alleged QAnon-supporter.”

QAnon, which first surfaced in 2017, rests on the baseless theory that Trump is fighting against a global network of billionaire pedophiles, devil-worshipping Democrats and baby-eating Hollywood stars and their “deep state” counterparts embedded in the U.S. federal government’s sprawling bureaucracy. A growing group of followers consumed and contributed to the false narratives first on the freewheeling social media site known as 4chan, then on other social media sites, fueled by what they thought were cues from “Q,” a secret intelligence official they believed was leaving clues about government corruption. It is not clear if “Q” even exists.

Many of the claims are dark and outlandish, and for years adherents to the theory were considered mostly fringe and not a significant threat. They had “keyboard bravado,” as one FBI special agent said last week, and were confined to the darkest corners of the web.

But recently, numerous violent incidents have been linked to people who support QAnon theories, and recent polling suggests that the conspiracy theories are reaching wider audiences than previously thought. For example, more than one in three Americans believe a so-called “deep state” is working to undermine Trump — another unfounded conspiracy commonly peddled by QAnon users — according to an NPR/Ipsos poll conducted in December.

For law enforcement officials seeking to prevent future violent attacks, the rise of QAnon is presenting fresh challenges. Authorities tasked with monitoring online extremism must now grapple with how to evaluate and combat emerging plots without infringing on constitutionally protected free speech.

“We have to separate the aspirational from the intentional and determine which of the individuals saying despicable things on the internet are just practicing keyboard bravado, or they actually have the intent to do harm,” said FBI agent-in-charge Steven D’Antuono during a press briefing last week.

In the wake of the Capitol attack, the FBI prepared a document meant to assist law enforcement partners in identifying QAnon “indicators” online, defining phrases and hashtags used by its followers. But the document also notes that “the FBI does not initiate any investigative activity based solely on the exercise of First Amendment activities.”

In a separate bulletin distributed to law enforcement partners on Jan. 13, the FBI warned that conspiracy-minded followers of QAnon may feel emboldened after the perceived “success” of the Capitol assault.

“Some [domestic violent extremists] view the 6 January event as a success, in conjunction with the potential to exploit follow-on lawful gatherings and ideological drivers — including conspiracy theories, such as QAnon — likely will also inspire some [domestic violent extremists] and others to engage in more sporadic, lone actor or small cell violence,” the bulletin warned.

Ahead of the inauguration, law enforcement officials are keeping a close watch on the threat posed by QAnon-aligned “lone wolves.” The Washington Post reported Monday that the FBI privately warned its partner agencies that QAnon adherents have discussed returning to Washington for Joe Biden’s swearing-in, posing as National Guard troops.

ABC News’ Alex Mallin contributed to this report.