Joshua A. James, 33, of Arab, Alabama, is at least the 11th person associated with the far-right militia to face charges in connection with the deadly Jan. 6 siege, which left five people dead and caused more than 130 police officers to be injured as they tried to protect the Capitol from a mob of former president Donald Trump's supporters.
Nine of the group's alleged associates are charged in a superseding indictment with conspiring to storm the Capitol as far back as November.
Earlier this week, Roberto Minuta, 36, was also identified as providing security to Stone before he allegedly stormed the Capitol. He is also facing criminal charges.
Stone, in a statement earlier this week, denied knowing Minuta, and said he had no advanced knowledge the Capitol would be attacked.
According to the charging documents, James was captured in photographs on Jan. 6 wearing tactical gear with Oath Keepers insignia.
"Publicly-available video also captured James inside the Capitol building," the complaint says.
James is due to appear in a federal court in Alabama on Thursday for a detention hearing. His public defender declined to comment.
More than 300 people have been charged so far in connection with the attack on the US Capitol, and the FBI has been increasingly focused on suspects with ties to right-wing extremist groups.