Inmates and prison workers are reporting unusual behavior from the 24-year-old sole suspect of the Aurora, Colo., movie theater shooting.

According to the New York Daily News, James Egan Holmes entered the prison dressed up like the Joker, "acting crazy" and "spitting on guards". The Daily News also reported that other inmates have threatened to kill Holmes.

“All the inmates were talking about killing him," just-released inmate Wayne Medley told the Daily News. "Everyone was looking for an opportunity. It’s all they could talk about."

Holmes is being held at the Arapahoe Detention Center in solitary confinement.

Meanwhile, authorities are still investigating and trying to disarm the suspect's apartment. A bomb squad managed to set off a controlled detonation on Saturday, but it's unclear how many booby traps he set.

According to witnesses, Holmes entered the theater during the first 30 minutes of the midnight premiere of "The Dark Knight Rises" at the Century 16 theater in Aurora, Colo. Some moviegoers thought that Holmes, who was wearing a gas mask and body armor, was part of the movie premiere.

Police said that he had planned the attack for months.