A Marine Corps officer was arrested Thursday for alleged crimes during the U.S. Capitol riot on Jan. 6, becoming the first known active-duty service member charged in the violent attempt to thwart the certification of Joe Biden’s election as president.

Maj. Christopher Warnagiris, 40, stationed at Marine Corps Base Quantico, was charged with five counts, including assaulting and obstructing police during a civil disorder and obstructing an official proceeding of Congress, federal prosecutors said. He made his first appearance in federal court in Alexandria on Wednesday afternoon.

The attack on the Capitol prompted the Pentagon to refocus efforts on weeding possible extremists out of the active-duty ranks, with a recent military-wide “stand-down” for service members to discuss the issue.

Warnagiris joined the Marine Corps in 2002 and serves as a field artillery officer, officials said. He served on four deployments, including in Iraq and Afghanistan. His current assignment includes training to “improve the warfighting skills” of senior commanders.

“There is no place for racial hatred or extremism in the Marine Corps,” said Maj. J.A. Hernandez, a Marine Corps spokesman. “Our strength is derived from the individual excellence of every Marine regardless of background. Bigotry and racial extremism run contrary to our core values.”

Four other people who have military ties and were charged in the riot serve part-time in the National Guard or Army Reserve. At least 42 others are military veterans, according to service records obtained by The Washington Post, of more than 400 arrested on federal charges.

An FBI agent attested that Warnagiris was the first individual to push himself through the East Rotunda doors about 2:25 p.m. on Jan. 6, after three other people who entered the Capitol from elsewhere pushed through police and tried to force the doors open from the inside.

Charging papers alleged that security camera footage shows that Warnagiris then used his body to keep the doors open, pulled others inside and pushed back an officer trying to shut the doors.

In a screenshot of security footage included in the FBI affidavit, Warnagiris, dressed in a dark jacket, “military green backpack” and black-and-tan gloves, allegedly appears to struggle with the officer, identified as A.W., who was trying to block doors.

A witness on March 16 identified Warnagiris to the FBI on the basis of photos the agency released of suspects wanted in the assaults on officers on Jan. 6, the FBI said.

Investigators said they corroborated Warnagiris’s identification through two government photographs of him and a co-worker at his military command who sees him several times a week and who recognized him from security and news footage of the event.

During his appearance in court Wednesday, he said he is seeking an attorney and was released on personal recognizance. The government did not seek to keep him detained.

In the first 120 days after the Jan. 6 riots, approximately 411 individuals have been arrested on federal charges, including more than 125 people charged with assaulting or impeding law enforcement.

Although the percentage of male veterans charged in the riot is roughly equal to the portion of male veterans in the U.S. population overall, analysts and experts have said that military connections are “force multipliers” for extremist and militant groups, bringing military training and social capital to the organizations and their causes.

Several far-right and extremist groups, such as the Oath Keepers and Proud Boys, participated in the riot and count veterans among their members.

Under a review launched by Defense Secretary Lloyd Austin, Defense Department officials are reexamining rules governing troops’ affiliations with anti-government and white supremacist movements, ties that currently are permissible to a limited degree.

Missy Ryan contributed to this report.