The dominos are beginning to fall in the conspiracy case against the Oath Keepers, after prosecutors flipped a member of the militia that allegedly helped plan the January 6 riots at the U.S. Capitol.

On Wednesday, Graydon Young, a member of the organization’s Florida chapter, pleaded guilty to two counts of conspiracy and obstruction of an official proceeding. According to ABC News, Young’s deal “includes a promise to provide cooperation in the government’s conspiracy case against 15 fellow members of the Oath Keepers, including testimony before a grand jury and at trial, in addition to an agreement to sit for interviews with law enforcement in their investigation into the group’s activities.”

Young will receive leniency for his cooperation – but he may have to testify against his sister, Laura Steele, who is also a member of the Oath Keepers. She had joined at Young’s urging.

Young, 54, served in the U.S. Army Reserve and U.S. Navy Reserve. He had joined the Oath Keepers just a month before the riot. The Wall Street Journal provides more details on the case against him:

Mr. Young “was preparing for a military-style confrontation or attack” on Jan. 6, prosecutors say. He and other Oath Keeper members allegedly moved through the crowd together in a tactical formation known as a stack, went up the center steps on the east side of the U.S. Capitol, breached the door and stormed the building. Court filings include photos of Mr. Young wearing military-style tactical gear and a helmet at the riot.

Before the assault, Mr. Young also arranged for a Florida company that provides firearms and combat training to train him and other members of the Oath Keepers, prosecutors say.

Elsewhere on Wednesday, Judge Royce Lamberth issued the first sentence against a January 6 defendant. Anna Morgan-Lloyd, 49, from rural Indiana, will serve probation for breaching the Capitol and leaving after ten minutes. She expressed remorse for her actions and condemned the violence, so her punishment is unlikely to reflect the forthcoming sentences of more recalcitrant members of the mob.

Judge Lamberth, a Reagan-appointee to the DC federal court, said lawmakers who have downplayed the riot are a “disgrace.”

“I don’t know what planet they were on,” Lamberth said, and added that videos “will show the attempt of some congressman to rewrite history that these were tourists walking through the capitol is utter nonsense.”

Last month, Rep. Andrew Clyde (R-GA) said “Watching the TV footage of those who entered the Capitol and walked through Statuary Hall, showed people in an orderly fashion in between the stanchions and ropes taking pictures. If you didn’t know the footage was from January 6, you would actually think it was a normal tourist visit.”