As authorities investigating the Jan. 6 attack on the U.S. Capitol continue to pore over images and video of the riot, they've encountered a distressing trend: A growing number of alleged perpetrators had previously served their country.

At least 52 active or retired military, law enforcement, or government service employees are among the over 400 suspects arrested for their alleged actions at the Capitol, according to an ABC News investigation based on military records, court records, interviews, and publicly available news reports. The arrests include over half a dozen ex-police officers and multiple former elected officials -- and represent some of the most significant and violent charges brought in connection with the deadly insurrection.

Mary McCord, a longtime national security official who now runs Georgetown University's Institute for Constitutional Advocacy and Protection, said extremism among those with military or law enforcement backgrounds is a serious problem that needs to be addressed immediately.

"I'm not really surprised that there is a substantial subset of defendants who come from these backgrounds," McCord told ABC News. "For veterans, the sense of mission is very important, so [Veterans Affairs] should be looking into how they can better serve veterans and help facilitate productive missions for them."

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But it's a tough challenge, said ABC News contributor and retired Marine Col. Steve Ganyard, because there is little data tracking the problem in real-time.

"How to come to grips with it is not easy for military leaders," Ganyard said. "Not only is it hard to isolate and quantify; there’s no clear means to fix it."

According to a report from Georgetown's Project on Extremism, military individuals who participated in the attack on the Capitol were about four times more likely to be involved in domestic extremist organizations, such as the Proud Boys or Oath Keepers, which are now being probed by the Justice Department over their alleged role in helping plan and carry out the assault on the Capitol. The Georgetown group identified 43 alleged Capitol rioters as having military backgrounds, and said that more than a third of them were affiliated with violent extremist organizations.

Some of those arrested said that their past experience provided a natural path into the world of militias. Laura Steele, an alleged Oath Keeper who's been charged as part of a sweeping conspiracy case against the paramilitary group, boasted about her previous law enforcement experience in her application to the group, according to court records.

"I have 13 years of experience in law Enforcement in North Carolina. I served as a k-9 Officer and a SWAT team member," Steele wrote on her application, according to court documents.

The majority of the 52 suspects with military, law enforcement or government experience were retired when they allegedly stormed the Capitol. Some had careers that gave them access to sensitive locations and prominent people.

During his career in law enforcement, retired New York Police Department officer Thomas Webster had provided security at both City Hall and the mayor's residence -- but despite that background in protecting government buildings and officials, Webster allegedly attacked a Capitol police officer with a metal flagpole in what federal prosecutors called a fit of "pure rage." Sara Carpenter, another retired NYPD officer, was also arrested for participating in the riot.

At least 10 individuals were still actively employed in their roles as police officers, local elected officials, and Army reservists when they allegedly helped storm the Capitol on Jan. 6.

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Jacob Fracker and Thomas Robertson were employed by the Rocky Mount Police Department in Virginia when prosecutors say they entered the Capitol and snapped a photo with their middle fingers extended, in front of the statue of Revolutionary War hero John Stark. They were later fired.

Federico Klein, who prosecutors allege was a "violent and enthusiastic" participant in the riot, was an active Trump administration appointee with a top security clearance at the time authorities say he attacked police officers on Jan. 6. He remained in his post for nearly two weeks after the attack before he resigned.

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Fracker, Robertson and Klein have all pleaded not guilty to the charges against them.

Some of those who allegedly participated in the attack have remained in their positions even after their identities were revealed and charges were filed against them.

Suzanne Ianni, who is facing charges of unlawful entry and disorderly conduct on Capitol grounds, remains a member of the governing board of Natick, Massachusetts, because officials say the town has no way of removing her. Ianni allegedly helped organize eleven busloads of people to travel to Washington D.C., according to court records, though it's not clear if it was for the march on the Capitol or the rally that preceded it.

MORE: Oath Keepers leader, during attack on Capitol, allegedly told followers 'Trump better do his damn duty'

In the days after the insurrection, Ianni said in an interview that she and her group were "expressing our First Amendment rights to protest an illegal election."

Three individuals charged in connection with the attack are still on active duty in the Army Reserve or National Guard, Army officials confirmed to ABC News. They include Fracker, the former Virginia police officer, who is a corporal in the Virginia National Guard, the Army said.

Fracker, charged with unlawful entry and disorderly conduct on Capitol grounds, pleaded not guilty to the charges against him.

Accused participant Timothy Hale-Cusanelli is a U.S. Army Reserve Sergeant who serves as a Human Resources Specialist. He was charged with multiple offenses, including violent entry and obstructing a law enforcement officer, and pleaded not guilty.

For many of those facing charges, a background in government service has proven to be unhelpful. In determining whether or not to detain Federico Klein, the Trump administration appointee, Judge Zia Faruqui pointed to Klein's military service and State Department employment as factors supporting detention.

Klein had "sworn [an] oath to protect the Constitution," but instead "switched sides" and joined the riot, Faruqui said.

"He should have known better," said the judge, before ordering him to be detained.

ABC News' Luis Martinez, Aaron Katersky, Alexander Mallin and Will Steakin contributed to this report.