James Holmes, the suspect accused of killing 12 people and injuring dozens more in last Friday's "Dark Knight Rises" massacre in Aurora, Colo., sent a notebook full of details about his plans for his attack to a psychiatrist as much as a week before the shooting.

Fox News is reporting from a law enforcement source that Holmes sent the notebook -- "full of details of how he was going to kill people" -- to a psychiatrist at the University of Colorado. But the notebook was not discovered until Monday after sitting unopened in its package in a mailroom.

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

Among the images were pictures of stick figures murdering other stick figures.

The source told Fox News the package had been in the mailroom since July 12, although another source says it is unsure when it was sent.

It is unclear why the notebook, now in the possession of the FBI, was sent to this particular psychiatrist, who was not named.