Inside the mind of Colorado theater shooter James Holmes

CENTENNIAL, Colo. -- For the first time, a Colorado jury has had a look inside the mind of a killer: The gunman who killed 12 people and left 70 injured when he opened fire in a crowded movie theater.

As James Holmes mounts an insanity defense, jurors were shown the notebook that he mailed to a psychiatrist shortly before the attack.

The spiral notebook has long been thought to hold clues to Holmes' state of mind at the time of the July 20, 2012 attack -- but this was the first look inside. Tuesday afternoon, excerpts were read aloud by Aurora Police Sgt. Matthew Fyles.

On some of the 29 pages, Holmes wrote rambling observations and questions, including "What is the meaning of life?", and, "What is the meaning of death?"

On several pages he repeated the question: "Why? Why? Why?"

On others, accounts of scouting several theaters in the days before the attack.

Holmes apparently considered attacking an airport but decided against it, not wanting his attack to be confused with terrorism.

"The message is there is no message," Holmes wrote, according to Fyles.

He chose a theater, even though Holmes put the chances of being captured "99 percent."

Jurors who will decide on a plea of "not guilty by reason of insanity," followed along in their own copies as Fyles read Holmes' writing aloud.

"The obsession to kill, since I was a kid, with age became more and more realistic," Holmes wrote.

He also said he had "decided to dedicate life to killing others so that I could live."

Holmes sent his notebook to his psychiatrist in a mailer with 20 different $20 bills -- all burned to some extent.

Also inside: A drawing of a circle with the numeral one and the infinity sign -- the same symbol found on a calendar inside Holmes' apartment the day of the shooting.

  • Jim Axelrod

    Jim Axelrod is the senior national correspondent for CBS News, reporting for "CBS This Morning," the "CBS Evening News," "CBS Sunday Morning," and other CBS News broadcasts.