Jon Ritzheimer on Monday admitted in federal court that he conspired to impede federal officers through intimidation, threats or force while participating in the armed takeover of the Malheur National Wildlife Refuge in January.

The felony charge carries a maximum sentence of six years in prison, but Ritzheimer faces between 2 1/2 and three years under sentencing guidelines, Assistant U.S. Attorney Craig Gabriel told the court. The government will recommend that Ritzheimer, who has no criminal history, be sentenced on the low end of that range, Gabriel said.

The 32-year-old, who lives in the Phoenix area, faced additional accusations of possessing a firearm in a federal facility and theft of government property, specifically taking cameras that belonged to the FBI. The government plans to dismiss those charges at his May 8 sentencing as part of a plea agreement.

The sentencing was scheduled for next spring so Ritzheimer and his defense attorney, Terri Wood, have time to gather materials and information that present mitigating circumstances before the hearing, Gabriel said.

Ritzheimer is the 11th of 26 standoff defendants to plead guilty in the federal conspiracy case that resulted from the 41-day armed takeover at the bird sanctuary outside Burns. As part of the agreement, Ritzheimer will also forfeit a shotgun that federal authorities seized during their investigation.

Jon Ritzheimer

U.S. District Judge Anna J. Brown went over Ritzheimer's plea agreement and petition in great detail. She asked whether he understood that he couldn't possess a gun or ammunition with a felony conviction and that he was surrendering his right to appeal.

"This really is the end of your case," Brown told him.

Ritzheimer said he understood. He wore a khaki-colored suit with a white dress shirt. He set his black sunglasses with blue-mirrored lenses in front of him on the defense table.

Before the Burns standoff, Ritzheimer was most widely known for anti-Islam protests he organized last year in Phoenix. They drew hundreds of people and caught the attention of the FBI. He also sold anti-Islam T-shirts through his apparel company, Rogue Infidel. The website now asks for donations to help Ritzheimer and his family.

Ritzheimer last September also threatened to arrest a Michigan senator for treason when he supported a nuclear deal with Iran, prompting an investigation by the U.S. Capitol Police.

Military records show Ritzheimer was in the Marine Corps Reserves from 2002 through 2014, serving two tours in Iraq as a motor transport driver. He has worked as a motorcycle mechanic.

Ritzheimer arrived at the refuge on Jan. 2 and left for home on Jan. 24, two days before Ammon and Ryan Bundy and other co-defendants in the case were arrested as they made their way to a community meeting in John Day.

Ritzheimer surrendered to the FBI in Arizona on Jan. 26 and was brought back to Oregon. A judge in March released him from custody and allowed him to return home to Arizona while his case was pending.

Prosecutors have said Ritzheimer was one of the leaders of the armed takeover. While at the Malheur refuge, Ritzheimer picked up mail, took meals to the other occupiers and served as a personal security guard to escort the Bundys to news conferences and meetings, according to court records.

During Monday's hearing, Gabriel told the court that Ritzheimer was part of the first group to arrive at the refuge, which was closed for the weekend on Jan. 2. He was armed when he and others first entered the headquarters. He then assumed a role as a security guard outside the refuge and told Ammon Bundy that they were "in control" of the property, Gabriel said.

Ammon Bundy and others had been part of a demonstration in Burns, protesting the federal arson case against father and son ranchers, Dwight Hammond Jr. and Steve Hammond, before they arrived at the bird sanctuary.

Gabriel said that during the takeover, Ritzheimer also used his personal truck to block the refuge gate.

After the prosecutor described Ritzheimer's conduct, the judge asked the defendant to explain what he did.

Ritzheimer told Brown that he was part of a "plan to take a protest to the next level." The judge inquired whether he was protesting because of the Hammonds.

"Yes," Ritzheimer replied. "We were protesting actually two things. Government overreach and the re-sentencing of the Hammonds."

Ritzheimer told that judge that he "forcibly occupied the refuge."

"I can see how my conduct and actions there would be intimidating," he said.

After his plea, Brown agreed to remove the GPS monitoring and curfew conditions from Ritzheimer's release agreement.

Ritzheimer left the courthouse with his attorney and a small group of reporters behind him. Commenting on his plea, he said, "Marines believe in integrity."

Maxine Bernstein, Carli Brosseau and Lynne Palombo of The Oregonian/OregonLive contributed to this report.

-- Rebecca Woolington

503-294-4049; @rwoolington