Washington CNN  — 

An alleged member of the Oath Keepers pleaded guilty on Wednesday to charges related to the January 6 insurrection, the first plea deal among the Capitol riot cases against extremist groups.

Graydon Young, a 54-year-old from Florida who went by “GenXPatriot,” is charged in a 16-person conspiracy case alleging members of the Oath Keepers plotted to carry out the January 6 insurrection.

It is the first guilty plea among any defendants in the major Capitol riot conspiracy cases and is a significant development as investigators continue to pursue leads on extremist groups that they believe planned for an armed attack to help then-President Donald Trump and stop Congress from certifying the 2020 election.

Young agreed to cooperate with federal investigators and cut a deal to plead guilty to two felony counts – conspiracy and obstruction of an official proceeding. He could face a likely sentence of more than five years in prison, according to estimates read at his plea hearing on Wednesday. He has also agreed to pay $2,000 in restitution for damage done to the Capitol building.

His plea deal factors in that the conspiracy involved extensive planning in scope and preparation, a major coup for prosecutors to secure as they continue to investigate the Oath Keepers stationing guns around the Capitol and coordinating their movements to attack Congress.

Prosecutors are dropping the aiding and abetting charges Young faces, as well as a charge he faced for deleting his Facebook account on January 8.

Young is among a pair of siblings charged in the Oath Keepers case who investigators say traveled to a Virginia hotel to attend pro-Trump rallies in Washington in early January.

Prosecutors allege he applied to become a member of the Oath Keepers group, a far-right coalition of largely ex-military and law enforcement that organized paramilitary training and attendance at political events, before January 6, and was posting on Facebook about recruiting for the group in December.

Prosecutors say Young was part of the “stack” military-style formation of Oath Keepers that cut through the crowd to move inside the Capitol.

Young’s co-defendants in the case are contesting their charges.

This story has been updated with details of Young’s plea agreement.