The U.S. Attorney’s Office is investigating militia involvement in the arrest of a man protesting the June 4 free-speech rally in downtown Portland, according to a spokesperson for Federal Protective Services, the police division of the U.S. Department of Homeland Security.

Photos and video circulating online show what appears to be federal officers working alongside a militia member to restrain a counter-protester on the ground near the perimeter of the “alt-right” white nationalist rally at Terry Schrunk Plaza on Sunday. The arrested counter-protester was one of thousands who showed up to decry the rally.

“The officers were in the process of removing an individual who was unauthorized in that part of the demonstration,” said Rob Sperling, director of communications and outreach for Federal Protective Service, which provides security at federal facilities.

Federal officers were “operating within the scope and within their authority,” Sperling said, “but the incident with the militia man in that photo is actually under review with the U.S. Attorney’s Office right now.”

Members of the Oath Keepers and Three Percenters militias provided security to attendees of the free-speech rally after Multnomah County Republican Party Chairman James Buchal publicly announced he beleived it would be appropriate for militia to provide security at Repubican events. Militia members were not allowed to bring weapons.

Although Buchal attended the June 4 rally, he said it was not a Republican Party-sponsored event, and he was not calling for militia to act as security at it.

A spattering of snapshots and short videos of the incident spread across different online platforms appear to show that an altercation between a militia member and a counter-protester led to the protester’s arrest by federal officers assisted by another militia member who appeared to be allowed to keep his hands on the protester for an extended period of time.

OPB digital producer Bryan M. Vance posted a series of photos to Twitter of the incident that began with a militia member wearing a black leather vest, who Vance described as an Oath Keeper named “Tiny,” grabbing the counter-protester.

Vance followed with photos showing a second militia member, wearing a camouflage helmet and bulletproof vest, helping federal officers restrain the counter-protester on the ground while Tiny stands nearby watching over the arrest.

Photos show this second militia member holding the back collar of the protester’s T-shirt with his right hand while holding the man’s shoulder with his left.

An Oregonian YouTube video shows the militia member retrieving zip-ties attached to the back of an FPS officer’s uniform so that officers could use them to handcuff the counter-protester.

A protester in attendence, Andrew Riley, posted a video of the incident on Twitter that begins with the militia member already assisting officers and continuing to crouch on the ground next to the detainee for an additional 45 seconds before appearing to help officers lift the man, now with his hands restrained behind his back, from the ground.

Sperling said, as policy, Federal Protective Services meets with organizers before events to go over the ground rules, including instructions to not to interfere with law enforcement.

He did not know if any militia members were present during that meeting or if Federal Protective Services was in communication with militia members prior to the event.

“We usually don’t want anybody interfering with an arrest,” he said.

Portland police employees did not allow militia to assist with any of their arrests, according to Portland Police Bureau spokesperson Sgt. Pete Simpson.

Oath Keepers and Three Percenters also descended on Berkeley, Calif., to provide security for a free speech rally in April after claiming the Berkeley police department failed to protect attendees from assault at a previous rally.

An Oath Keeper at the June 4 free speech rally in Portland. Photo by Diego Diaz

These two militia groups are considered to be “extreme anti-government” by the Southern Poverty Law Center.

According to a 2016 report from Rural Organizing Project and Political Research Associations, the Three Percenters (often shortened to III%), along with the Oath Keepers, participate in vigilante border militias, spread anti-Muslim rhetoric and “tend to be more aggressive and violent than other Patriot movement groups.”

The report, “Up in Arms: A Guide to Oregon’s Patriot Movement,” states there are thousands of Patriot activists in Oregon and that the Three Percenters surfaced shortly after the 2008 election of Barack Obama.

According to SPLC, Three Percenters United Patriots and American Patriots Three Percenters are both a statewide presence in Oregon, and the Oath Keepers are present in 10 counties, including Washington, Columbia, Lane and Marion.

Kevin Sonoff, a spokesperson for the U.S. Attorney’s Oregon District Office, said in an email, "Per Department of Justice policy" he could neither confirm nor deny the existence of an investigation into Sunday's arrest.

Portland police did not immediately respond to inquiries about the identity of the arrested protester. This story will be updated as details become available.

Correction: A previous version of this article incorrectly stated Multnomah County Republican Party Chairman James Buchal had publicly welcomed the militia groups as security at the June 4 rally. He told Street Roots that Multnomah County Republican Party is weighing the option of having Oath Keepers at future events, however the June 4 rally was not a Republican Party event and he did not invite militia to provide security at it. Street Roots regrets the error.