The man, Graydon Young, is one of 14 members of the Oath Keepers group charged with taking part in the assault on Congress, which left five people dead, including a Capitol Police officer.
Young, a 54-year-old resident of Englewood, Florida, told U.S. District Judge Amit Mehta he was pleading guilty to one charge of conspiracy and one of obstructing an official proceeding. Young is the brother of Laura Steele, 52, of Thomasville, North Carolina, who also faces charges in the case.
He agreed to cooperate with investigators as part of his plea deal. Questioned by the judge about the extent of his possible cooperation, Young agreed to give grand jury testimony and to be interviewed by law enforcement investigators without his lawyers being present.
The judge did not impose a sentence at Wednesday’s hearing and allowed Young to remain on bail pending a further hearing later this summer.
More than 480 people have been arrested and charged with taking part in the unrest, which saw rioters smash windows, battle police inside and outside the Capitol and sent lawmakers and then-Vice President Mike Pence into hiding.
Another defendant, Robert Reeder, pleaded guilty on Wednesday to one misdemeanor charge of parading, demonstrating or picketing in a Capitol building.
A judge on Wednesday is also scheduled to hand down the first criminal sentence to one of the Capitol rioters. Anna Morgan-Lloyd, 49, of Bloomfield, Indiana, agreed last month to plead guilty to a single charge of parading, demonstrating or picketing in a Capitol building. Federal prosecutors have recommended three years of probation, a $500 fine, and 40 hours of community service.
The riot followed a fiery speech in which Trump repeated his false claims that his election defeat was the result of widespread fraud and disrupted the formal count by Congress of electoral votes in the race.
Federal prosecutors said in court papers that Young on Dec. 22 made plans to fly from Florida to North Carolina on Jan. 4, with a return trip on Jan. 8. On Dec. 26, prosecutors said, he wrote to a Florida company engaged in firearms and combat training: “I have joined Oath Keepers. I recommended your training to the team. To that effect, four of us would like to train with you.”
The indictment says Young and eight other indicted Oath Keepers pushed their way in a “stack” up the steps on the east side of the Capitol building.
The Oath Keepers are a loosely organized group of activists who believe that the federal government is encroaching on their rights, and “explicitly focus” on recruiting current and former police, emergency services and military members.
Reeder, a 55-year-old Maryland resident, pleaded guilty to one misdemeanor charge of parading, demonstrating or picketing in a Capitol building. He faces a maximum of six months in prison.
During a court hearing, Reeder’s attorney stressed that his client “didn’t touch anything” or “destroy anything” or “physically engage in any kind of resistance” while he was inside the Capitol.
He is due to be sentenced on Aug. 18.
Also on Wednesday, Eduard Florea, a supporter of the Proud Boys movement who was accused of keeping a large weapons cache and making social media threats related to the attack, was denied bail, despite evidence of what his lawyer said were signs of chronic kidney disease. Florea was not in Washington on Jan. 6. Reporting by Mark Hosenball; Additional reporting by Sarah N. Lynch, Jan Wolfe and Jonathan Stempel; Editing by Scott Malone, Jonathan Oatis and Bill Berkrot