The man accused of shooting 70 people in an Aurora movie theater, killing 12 of them, is being held in isolation at the Arapahoe County Jail.Undersheriff David Walcher told 7NEWS James Holmes is being held in administrative segregation, with no contact to other inmates, due to the nature of the case against him.A source inside the jail told 7News Holmes had referred to himself as "The Joker"; however, deputies have not confirmed that. Walcher said he had not heard reports of Holmes being disruptive but he has not been inside the jail where Holmes is.Several family members and friends of inmates spoke with 7News outside the jail on Sunday. They were told the inmates are aware Holmes is inside the jail, but most have not seen him.Roseann Drury, a girlfriend of one inmate, said, "They know he's being held in another area for his own protection I guess. I think if he was released around the other people, obviously like everyone else they would be pretty upset with him."A law enforcement official said investigators found a Batman mask inside Holmes' apartment. The official spoke to The Associated Press on Sunday on condition of anonymity because he was not authorized to speak to the news media.Holmes displayed behavior that a gun range owner thought was "bizarre," but it is still unclear if anyone at the university where he studied had any hint of his plans. Police said James Holmes began buying guns at Denver-area stores nearly two months before Friday's shooting. He also received at least 50 packages in four months at his home and the University of Colorado that authorities are investigating to see whether they contained materials for the potentially deadly booby traps that police found in his apartment. At the same time, the quiet 24-year-old was in the final weeks of the first year of a rigorous Ph.D. neuroscience program, where he took a three-part final exam required for students to progress in the program and was scheduled to give a presentation on MicroRNA Biomarkers before abruptly leaving in June. Holmes is being held without bond on suspicion of multiple counts of first-degree murder after a shooting rampage minutes into a premiere of "The Dark Knight Rises" in Aurora early Friday that left 12 people dead and 58 injured. He is scheduled for an initial hearing Monday in Arapahoe County Court and has been assigned a public defender.