A federal officer who was initially detained and arrested at Saturday's Capitol rally, known as Justice for J6, will not be charged. The law enforcement officer was arrested with a firearm and will not face charges.

A 27-year-old man from New Jersey, the man is an agent with US Customs and Border Protection. His arrest, at the hands of a Capitol Police officer, was for illegal gun possession on Capitol grounds. Four were arrested in total.

Capitol Police arrested two suspects for felony extraditable warrants from Texas; one was for possession of a fire arm and the other was for a probation violation. Another man was arrested for weapons violations.

Footage was taken off the arrest by News2Share editor-in-chief and documentarian Ford Fischer. It shows Capitol Police surrounding a masked man. "He tells them where the gun is, and they pull out his badge," Fischer said. "He's undercover law enforcement. Without disarming or handcuffing him, police extract him from the event."

The US attorney's office said that they were "not moving forward with charges," but further information was not forthcoming. Other officers who were present told the AP that the man who was arrested was not at the rally under the auspices of his function as a law enforcement officer. These officers chose not to give their names.

Customs and Border Protection reported that they are "fully cooperating with the investigation." In a statement, they said that "CBP stresses honor and integrity in every aspect of our mission and expects officers to adhere to the oath they take to uphold the laws of this country."

The Saturday rally was meant to support those who had been arrested on charges stemming from the January 6 Capitol riot, many of whom are still being held pending trial or plea deal.

The events of Saturday were of concern to law enforcement, who put up fencing around the Capitol that had gone up and come down in the months following the Capitol riot.

Some congressional offices were closed, and both the US House and Senate were not in session. The Capitol Police had requested an additional 100 National Guard troops to help should the need arise. It did not.

"Still seems like more press than protesters. Less than one demonstrator per member of Congress as the scheduled event begins," NBC News' Jonathan Allen reported.

The rally remained peaceful, and drew less than 100 attendees. The number of reporters and law enforcement officers was not immediately tallied. The rally in Washington ended without major incident.