Dylann Roof, who is charged in the shooting of nine black parishioners at a church in Charleston, South Carolina, was reportedly assaulted in jail on Thursday.
Inmate Dwayne Stafford assaulted Roof as he was preparing for a shower, The Charleston County Sheriff's Office said in a news release. Roof, 22, sustained minor bruising to his face and back and doesn't want to pursue criminal charges, the release said.
He was examined by medical professionals and returned to his cell after the incident.
Roof could face the death penalty pending the outcome of trials in federal and state courts over the June 17, 2015, massacre at Emanuel AME Church.
Stafford, 26, is awaiting trial on first-degree assault and strong-armed robbery charges, The Associated Press reported.
Officials are investigating how Stafford was able to get out of his cell and down the stairs to Roof, the AP said, noting that the electronic cell doors can only be opened by officers at a control console.
"It seems to me pretty obvious at this point that at the very least we have complacency," Charleston County Sheriff Al Cannon said, according to the AP. "We do things day-in and day-out and they become routine."
A deputy assigned to the unit intervened in the assault while another deputy was on break, The New York Times reported.
Roof is accused of trying to start a race war via the June 2015 attack, which prosecutors say he plotted for months. His federal trial is set for November.