A report has said that James Holmes accused of killing 12 people at a Colorado cinema had posted a notebook detailing his plans to a psychiatrist at his university before the attack.
Police sayHolmes opened fire on a midnight screening of a Batman film in the Denver suburb of Aurora, killing 12 people and wounding 58 others.
A Fox News report said police and FBI agents were called to the University of Colorado Anschutz medical campus in Aurora on Monday after a university psychiatrist reported receiving a package believed to be from the suspect.
Although that package turned out to be from someone else and harmless, a search of the Campus Services' post room turned up another parcel sent to the psychiatrist with Mr Holmes' name in the return address.
After obtaining a search warrant, police took the package away and discovered its contents.
Fox News quoted its source as saying: "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."
Fox News did not identify the psychiatrist.
University spokeswoman Jacque Montgomery confirmed that a suspicious package was delivered to the campus on 23 July and said it was "immediately investigated and turned over to authorities within hours."
"The anonymous Fox News source that the package was received on 12 July and sat on a loading dock is inaccurate," Ms Montgomery said in the statement.
She declined to discuss the package any further, citing an order by Aurora County District Judge William Sylvester.
A spokesman for the FBI's Denver office said they could not speak about any aspect of the investigation.
The judge in the case issued a protective order this week that strictly limits what attorneys, law enforcement and court staff can say publicly about the case.
Mr Holmes, 24, was a doctoral student in neuroscience at the Anschutz campus until filing paperwork to drop out in June.
He made his first appearance in court on Monday, appearing sleepy and disoriented.
Authorities plan to formally charge him on 30 July.
