Authorities hope to find some clues about the motives of the alleged Aurora cinema shooter after discovering a document he posted to the University of Colorado.
The package, sent to a faculty member at the medical campus before the shooting, was turned over to the police on Monday.
James Holmes, who is accused of killing 12 people and injuring 58 others, had recently dropped out of a neuroscience graduate programme at the university.
US President Barack Obama is pledging to work with all parties on reducing gun violence, but shied away from advocating gun control.
“[But] I also believe that a lot of gun owners would agree that AK-47s belong in the hands of soldiers, not in the hands of criminals. That they belong on the battlefield of war, not on the streets of our cities,” Obama said.
Star of the new Batman movie ‘The Dark Knight Rises’ Christian Bale visited a memorial outside the Aurora cinema for the victims who were killed as they watched a screening of the film last Friday.