Those who know Loughner say he is a loner - alienated and unstable.
Debbie Schiedemantel taught Loughner at Pima Community College.
"He was just bizarre and strange," she said.
Last September, after an angry anti-government rant one day in class, she called the police.
"I was worried about my safety and the safety of other students," she said.
Loughner left an online trail of anti-government videos. On a YouTube slideshow, he wrote, "the government is implying mind control and brainwash on the people by controlling grammar."
On the morning of the shooting, Loughner apparently typed "goodbye" and "Dear friends ... Please don't be mad at me," on his MySpace page.
Authorities tell CBS News that Loughner's attack on Congresswoman Giffords was not partisan. He went after her, they think, because she was a symbol of government.
He may also have been upset after reportedly asking Giffords this question at a 2007 event, "What is government if words have no meaning?"
Giffords did not answer.
Bryce Tierney, Loughner's former friend says he never got over it.
"He seemed to dwell on the fact that she wouldn't answer his question. I think that was the start of it," Tierney told Erica Hill of "The Early Show."
Investigators found an envelope in a safe inside Loughner's home on Sunday.
On it was Congresswoman Gifford's name and the words, "I planned ahead," and "my assassination." Officials say Loughner signed it.
Loughner used a 9 millimeter semi-automatic pistol he bought at a Tucson sporting good store on November 30, 2010 for $500. The purchase was legal. CBS News has learned that he had at least 90 bullets.
The 22-year-old lived with his parents in a middle-class Tucson neighborhood where they seemed to have few friends.
Roger Whithead, Loughner's neighbor said, "People are so isolated now you don't know who's living next to them - you really don't."
Despite his anti-government feelings, Loughner tried to enlist in the Army, but he was rejected for ailing a drug test. He was suspended from community college on Sept. 29th, 2010 because of his erratic behavior. The school told him he needed a mental health evaluation to return. Loughner dropped out.
"He clenched his fists a lot and grinned," former classmate Steven Cates said. Cates wasn't surprised when he heard what Loughner allegedly did. He was so afraid Loughner would bring a gun to class some day that he tried to be friends with him so he wouldn't get shot.
"It was very apparent that he was not on the same level as everyone else."
The site of the shooting in Tucson is still blocked off and CBS News learned late this afternoon that the FBI has security camera video that captured at least part of the shooting spree on Saturday.