THOMAS: And sources say his postings on the Internet suggest his murderous rampage was premeditated. Only hours before the shootings, he allegedly posted a MySpace message entitled "Good-bye, Friends." It begins, "Dear friends, please don't be mad at me."
But why would a young man from suburbia slaughter so many? Loughner appears to have been obsessed with violence and was apparently at the government. He listed this YouTube posting as one of his favorites, "Let the Bodies Hit the Floor."
He appears paranoid, suggesting the government was monitoring his communications. "I know who's listening," he wrote. He also discusses mind control and brainwash methods.
DUPNIK: I have no reason to believe that the person was insane. Was he unstable? I would agree with that.
THOMAS: His neighbors, Vick and Amelia Cruz (ph), were horrified.
V. CRUZ (ph): I thought it was just a total disgrace. I mean...
A. CRUZ (ph): Especially to...
V. CRUZ (ph): ... what, a 9-year-old child? That was -- that hurt.
A. CRUZ (ph): A 22-year-old kid just through his life away and took how many with him?
THOMAS: They wondered, had signals been missed?
V. CRUZ (ph): There's got -- there should have been red flags, you know?
A. CRUZ (ph): The things he put on the Internet, and nobody noticed that there might be a concern?
THOMAS: Former high school classmates say Loughner never fit in.
(UNKNOWN): He is just off to himself and more of an outcast.
(UNKNOWN): A lonely kid just off to himself.
THOMAS: One friend he did manage to make, Caitlin Parker, said he became more peculiar in recent years. She recalled a strange encounter he once had with a wounded congresswoman.
PARKER: As I knew him more and more after high school, he got a little bit more odd. I mean, he was obsessed with the 2012 prophecy. I mean, he met Gabrielle Giffords once in '07 and told me he asked her some question that made absolutely no sense to me, but he said, "I can't believe she doesn't understand it. Politicians just don't get it."
THOMAS: Life for Loughner was punctuated by failure. After high school, he tried to enlist in the Army, but was rejected. Police say he toyed with drugs in 2007. In college, he made classmates uncomfortable.
COOROUGH: One woman had a poem that had something to do with an abortion, and he made a comment to the effect of she was like a terrorist killing the baby, and then laughed about that.
THOMAS: Last fall, he was suspended from college after school officials found a rambling incoherent YouTube video posted by Loughner. They told him, if he wanted to return, he would need to obtain a mental health evaluation.
By then, Loughner was known to police.
DUPNIK: There have been law enforcement contacts with the individual where he made threats. When you look at unbalanced people, how they are -- how they respond to the vitriol that comes out of certain mouths about tearing down the government, the anger, the hatred, the bigotry that goes on in this country is getting to be outrageous. And, unfortunately, Arizona, I think, has become sort of the capital. We have become the Mecca for prejudice and bigotry.
THOMAS: The FBI has begun to dissect Loughner's background, and a massive manhunt has been launched to look for the potential accomplice in the surveillance photo. The investigative task force includes not only the FBI, but local and state police and a cadre of federal agencies.