A crowd of Trump supporters gather outside as seen from inside the U.S. Capitol on January 6, 2021 in Washington, DC.
CNN  — 

Brian Ulrich, one of the 11 members of the Oath Keepers facing sedition-related charges, pleaded guilty to “obstruction of an official proceeding” and seditious conspiracy in federal court on Friday, becoming the second person to plead guilty to the gravest charges to emerge from the January 6, 2021, US Capitol attack.

According to the plea agreement, Ulrich, 44, will cooperate with the Justice Department in its historic prosecution against the far-right extremist organization. He could face more than six years in prison, according to the deal read aloud during Wednesday’s hearing, but prosecutors may ask for a lower sentence depending on Ulrich’s level of cooperation.

The guilty plea is another major step in the criminal case against the Oath Keepers, as prosecutors work to show how they believe the group of men plotted to stash weapons across the Potomac River, go to the Capitol and stop Congress’ certification of the Electoral College vote. The case has grown dramatically over the past year, relying in part on explosive private messages between Oath Keepers leaders, video of the group from the week they were in DC, and the cooperation of at least six other Capitol riot defendants with ties to the Oath Keepers organization.

The plea comes nearly two months after fellow Oath Keeper Joshua James, who served as private security for right-wing figures around January 6, pleaded guilty to sedition-related charges.

“Did you do that, agree with [Oath Keepers leader Stewart] Rhodes and develop a plan to stop the lawful transfer of presidential power, by force, on January 6, 2021” US District Judge Amit Mehta asked during the hearing on Friday.

“Yes, your honor” Ulrich said.

Rhodes, who is also charged with seditious conspiracy, has pleaded not guilty.

Ulrich, who at times appeared to be crying during the hearing, also agreed that he “intended to influence and affect conduct of the United States government and to retaliate against the United States government.”

At one point, Mehta asked whether Ulrich needed time to gather himself. Ulrich initially declined, saying that “it’s not going to get any easier,” but later accepted – taking a moment to audibly weep and gasp for air.

Ulrich, who is from Georgia, was part of an Oath Keepers leadership Signal chat where he, Rhodes and others planned for January 6. The messages, which are quoted in court documents, show how Ulrich repeatedly asked about bringing guns to DC as part of a quick reaction force.

“Someone can tell me if I’m crazy but I’m planning on having a backpack for regular use and then a separate backpack with my ammo” Ulrich messaged the leadership chat in late December, adding that “I will be the guy running around with the ‘budget AR.’” In another message days later, Ulrich asked Joshua James about firearms and a potential plan to “stage them in VA.”

Other messages that Ulrich sent to members of the Georgia Oath Keepers said that “civil war” might be necessary if then President-elect Biden was inaugurated.

“We must win. We must defeat these radicals,” Ulrich wrote in one message, “there’s treason at work here. When someone committed treason it used to mean something. you used to pay with your life!” In another message, Ulrich referenced a “Ruby ridge scenario that we can rally behind.”

Ulrich, James, and Oath Keeper Mark Grods traveled together to DC on January 4. In his own plea agreement, James admitted to bringing a semi-automatic handgun on the trip, and said Grods and others brought firearms, including a rifle, a shotgun, a semi-automatic handgun, and ammunition to a Virginia hotel. Grods has also pleaded guilty and is cooperating with the investigation.

On January 6, Ulrich, James, Grods and others rushed to the Capitol in golf carts during the siege, swerving around law enforcement. When they arrived, the group maneuvered through the mob with their hands on each other’s shoulders and eventually breached the building.