Movie-shooting trial to begin

CENTENNIAL, Colo.

- James Holmes was growing volatile well before he put on a gas mask and body armor, strapped on a rifle, shotgun, pistol and ammunition, and slipped into a midnight premiere of the Batman film "The Dark Knight Rises."

He was a sought-after neuroscientist-in-training, but he was falling apart. He told a classmate that he wanted to kill people, prosecutors say. He fell out of favor with his professors, who suggested he find a new career. He stopped seeing his psychiatrist, then sent her text messages so threatening that she alerted University of Colorado campus police. He even mailed her his journal, in a package with burned $20 bills.

Months before Holmes, 27, opened fire on the audience on July 20, 2012, killing 12 and injuring 70 more in one of America's deadliest mass shootings, the doctoral student was preparing for violence.

He stockpiled weapons, ammunition, teargas grenades and riot gear, and rigged his apartment to become a potentially lethal booby trap, cranking techno music in an apparent attempt to lure someone into opening his door.

Many observers hope Holmes' death-penalty trial that begins today will finally show what turned a seemingly dedicated scholar into a sadistic killer. Prosecutors have suggested he was angry over his academic decline. But anyone looking for a trigger or tipping point with mass killers is usually disappointed, said J. Reid Meloy, a forensic psychiatrist at the University of California, San Diego.