Charges against police officers, public safety workers and military veterans in the Jan. 6 insurrection at the Capitol have reignited concerns among lawmakers and law enforcement officials about violent extremists infiltrating government agencies.

Out of 324 arrests in the Capitol riot so far, 43 are current or former first responders or military veterans. At least four police officers and three former officers face federal charges. Two have been fired, one resigned and one was suspended without pay. Each of the officers charged has either pleaded not guilty or not yet been arraigned.

The alleged participation of public safety officials who have sworn to uphold the Constitution has led lawmakers to sound the alarm.

“A street alliance among right-wing paramilitary forces, law enforcement and demagogic politicians has been a hallmark of fascism for a century, so the involvement of multiple law enforcement officers from across the country in waging the Jan. 6th insurrection against the Capitol and the Congress is a warning sign of danger for our democracy,” Rep. Jamie Raskin, D-Md. “Off-duty cops beating up on-duty cops to overthrow an election is a nightmare scenario for America.”

The Capitol insurrection, where 140 police officers were injured and three later died, featured numerous examples of violent extremism and white supremacy. Rioters carried Confederate flags and nooses, and wore shirts saying the deaths of six million Jews during the Holocaust weren’t enough. Amid the crowd, law enforcement officers reveled in social media posts about how they “attacked the government,” according to court documents.

People involved in a number of hate groups have been arrested since the Capitol assault, including: 16 defendants linked to Proud Boys, a misogynistic, anti-immigrant and anti-Semitic group with ties to white supremacism,13 linked to QAnon, a once-fringe internet conspiracy movement that recently grew into a powerful force in mainstream conservative politics, 12 linked to Oath Keepers, a paramilitary organization that recruits current and former military, law enforcement and first-responder personnel

Some arrests also included people allegedly associated with the Three Percenters, an anti-government militia movement, and Super Happy Fun America, a group with ties to white nationalists known for organizing a “straight pride” parade in Boston.

Concerns about white nationalists infiltrating police departments have percolated for years. A 2006 FBI report warned that “white supremacist presence among law enforcement personnel is a concern due to the access they may possess to restricted areas vulnerable to sabotage and to elected officials or protected persons, whom they could see as potential targets for violence,” as happened at the Capitol.

“Their presence in law enforcement impedes official responses to right-wing terrorism, places loyal officers in peril, and exposes vulnerable communities to lawless violence by white supremacists dressed in blue,” said Raskin, who has investigated the infiltration of white supremacists in law enforcement as chairman of a House Oversight and Reform subcommittee.

Raskin has asked the FBI for a briefing about white supremacists infiltrating law enforcement by March 26, saying he was concerned the FBI lacks an adequate strategy to respond to the threat to public safety.

The FBI acknowledged receiving Raskin’s letter, but declined further comment.

“It’s alarming that the FBI has been unwilling to level with the American public and Congress about the full magnitude of the threat of domestic white supremacist infiltration of local police departments,” Raskin said. “We await a comprehensive strategy on how federal law enforcement plans to cut the links between law enforcement and right-wing extremist elements, including militia groups like the Oath Keepers and the Proud Boys. There is no excuse for further passivity and denial in the face of clear complicity between officers and self-fashioned storm troopers.”

FBI Director Christopher Wray told the Senate Judiciary Committee on March 2 that “the Capitol attack involved violent extremists” and that the FBI considered it “a form of domestic terrorism.”

He had warned presciently six months earlier that domestic violent extremism was driven by perceptions of government or law enforcement overreach, racism, anti-Semitism and misogyny. And he said domestic terrorism cases investigated each year doubled during his three years on the job.