A founding member of the far-right Oath Keepers organization accepted a plea deal and confessed to his participation in the Capitol insurrection, making him the first rioter to do so.

During a court hearing on Friday (April 16), Jon Ryan Schaffer — a heavy metal guitarist from Indiana — pleaded guilty to obstruction of an official proceeding, and entering and remaining in a restricted building or grounds with a deadly or dangerous weapon.

“Schaffer admitted to being among the first individuals to push past the damaged doors and into the Capitol building, forcing officers to retreat,” the Justice Department said in a news release.

“Schaffer and others advanced toward five or six backpedaling USCP officers while members of the mob swelled inside of the Capitol and overwhelmed the officers.” He also wore a tactical vest and carried bear spray as he attempted to block the Congress from the certification of election votes.

Schaffer’s admission is the first guilty plea in the ongoing probe of the Capitol siege. Per his agreement, he will now cooperate with the Department of Justice throughout the rest of the investigation and may even testify in other related cases. Based on his cooperation, Judge Amit Mehta, who is overseeing the case, will determine his sentence, which may be anywhere between 3.5 and 4.5 years. A typical obstruction charge carries a maximum sentence of 20 years; those with weapons charges usually serve up to 10 years in jail.

For now, the judge has approved Schaffer’s release from prison. When he is freed from custody, he will be allowed to travel within the lower 48 states. He is prohibited from carrying any firearms.

Schaffer was arrested in January and initially charged with six crimes in connection with the siege. Hundreds of rioters have been arrested and charged for their participation in the insurrection. According to USA Today, 12 of those people were members of the Oath Keepers.