James Holmes, accused of killing 12 people and wounding 58 others in a shooting last week in a Colorado move theater, sent a package detailing his plans to a psychiatrist at the University of Colorado. Unfortunately the notebook wasn't discovered until Monday after almost a week of sitting in the mailroom, a source told FoxNews.com.

A law enforcement source told Fox News that a notebook in the package, which had been in the university's mailroom since July 12, depicted a stick figure shooting other stick figures, among other violent scenes. It was not discovered until Monday and is currently in the hands of the FBI.

Inside the package was a notebook full of details about how he was going to kill people, the source said. There were drawings of what he was going to do in it -- drawings and illustrations of the massacre.

Holmes failed an exam in the weeks before the shooting and had dropped out of the University of Colorado-Denver, notes CBS News. He's been described as someone with a brilliant mind who hadn't lived up to his potential. An administrator said he had a poor work ethic and mediocre grades.

The psychiatrist the package was addressed to was not confirmed to have treated Holmes during his time at the school. The sources cited by Fox News said the intended recipient was also a professor at the university who treated patients at the psychiatry outpatient facility.

After allegedly carrying out the massacre at a midnight screening of The Dark Knight Rises Holmes was arrested by police in the parking lot of the movie theater in Aurora. At the time police descended upon him, Holmes was taking off his body armor and reportedly was surprised at how quickly law enforcement found him.

Holmes was also found to have rigged his apartment with explosives set to kill anyone that tried entering through the doorway. He also left music playing at a high volume, a strategy that perhaps was designed to cause a diversion for police. Reports have surfaced that the apartment was booby-trapped to the point that if detonated, the explosives would have taken down his entire building while the other residents were mostly asleep.

Holmes could face the death penalty and has been held in solitary confinement since his arrest, where he's also been threatened by other inmates. Aurora's chief of police, Dan Oates, has said Holmes has lawyered up and is refusing to cooperate with investigators.