James Holmes currently has a cell block to himself in Colorado's highest-security state prison—but he was still assaulted by another inmate. Department of Corrections officials have confirmed to the Denver Post that the mass murderer was attacked by inmate Mark "Slim" Daniels in a hallway, who lunged at Holmes while he was on his way to the day hall where he is allowed to spend four hours a day. Daniels, 27, is serving time for offenses including menacing, auto theft, and assault and will now be charged with assaulting Holmes, who wasn't injured, and a guard who intervened, reports the Post, which says it was alerted to the incident earlier this month by a letter from Daniels himself. Holmes is serving life without parole for the 2012 Dark Knight theater massacre. (More James Holmes stories.)