The leader of a militia group that had been detaining asylum-seekers in New Mexico at gunpoint was beaten in jail, according to the man’s lawyer and a sheriff’s department.

Larry Hopkins, 69, was “jumped and beaten by fellow detainees,” according to a letter his lawyer sent to the jail on Wednesday. Hopkins, who also goes by the alias Johnny Horton Jr., was arrested Saturday on suspicion of being a felon in possession of a firearm and ammunition.

Hopkins led the United Constitutional Patriots, whose members, some armed, held migrants who had crossed the border with Mexico until Border Patrol agents arrived.

Larry Mitchell Hopkins Dona Ana County Detention Center

“I talked to him afterwards yesterday and he was beaten, bruised, injured, dazed — and thoroughly demoralized,” Attorney Kelly O’Connell wrote to the Doña Ana County Detention Center.

A spokesperson for the Doña Ana County Sheriff’s Department said in a statement Wednesday that an "alleged battery" at the county jail was under investigation.

Spokeswoman Kelly Jameson said in a statement that the incident occurred after 9 p.m. on Monday and that the reported victim was Hopkins.

He was treated for non-life-threatening injuries, Jameson said, and transferred Tuesday from the jail by the U.S. Marshals Service.

O’Connell wrote that he was deeply concerned over the “violent attack.”

“Mr. Hopkins’ case is certainly high profile, and he has developed a controversial reputation because of his border activities,” he wrote.

Hopkins has been described as the "commander" of the United Constitutional Patriots, and the group's actions, posted as videos to social media, has drawn an outcry from the local police chief, politicians and activists.

Hopkins' arrest Saturday stemmed from gun charges based on reports to an FBI tip line about "alleged militia extremist activity" at his home in Flora Vista, New Mexico, and a subsequent visit to his residence by FBI agents, according to a criminal complaint.

In describing reports to that tip line, the FBI agent who wrote the complaint said Hopkins allegedly said the group was "training to assassinate George Soros, Hillary Clinton, and Barack Obama."

O'Connell has said that accusation is "categorically false" and questioned the timing of Hopkins' arrest.

On Tuesday afternoon, the Union Pacific railroad company determined it owned the land where the United Constitutional Patriots had been camped out and asked remaining members to vacate. A short time later, the last members of the group peacefully left the property and cleared the camp. Three people remaining at the camp sought to distance themselves from Hopkins and the United Constitutional Patriots, saying they were "citizen journalists" documenting the border crisis.

A spokesperson for the United Constitutional Patriots has described the group as aiding in immigration enforcement as the "eyes and ears of Border Patrol."

Customs and Border Protection has said it "does not endorse private groups or organizations taking enforcement matters into their own hands."