For months, Jared Lee Loughner creeped out classmates and teachers with his odd behavior.
As a student at Aztec Middle College in Tucson, Arizona, Loughner was prone to sudden outbursts in class, teachers said. He'd ask "incoherent" questions and make inappropriate comments.
Other times, he would just stare into space.
"He had an intense stare, but he usually didn't stare at other people," said Kent Slinker, who taught an "Intro to Logic" class attended by Loughner. "He would have a focused stare some place else in the room, and almost as if he was viewing another scene or intensely thinking about something."
Loughner often spoke out of turn and asked questions unrelated to the class topic, leading Slinker to assume the student had Tourette Syndrome.
"I was never able to talk to him on a one-to-one basis and I did worry about him a lot," he said. "I do recall thinking I hope his parents know what's going on and that they have a handle on things."
Loughner was arrested in Saturday's shooting at a constituents gathering held by U.S. Rep. Gabrielle Giffords in front of a Tucson Safeway grocery store. Six people died and more than a dozen were wounded. Federal authorities have charged Loughner with first-degree murder, attempted murder counts and attempting to kill a member of Congress, counts that involve shooting federal employees. State prosecutors also could bring charges related to other victims.
Interviews with friends and former teachers and classmates provide a glimpse of how he appeared in public - a little off, but not necessarily threatening. Background checks reveal brushes with the law that alone did not set off any alarm bells, a law enforcement official told CNN. He was also suspended from community college in September with the understanding that he could return if he obtained a clean bill of mental health from a doctor, school officials said.
On their own, the incidents prompted as much action as school officials or law enforcement felt necessary, given the cirumstances. Whether anyone ever put them all together remains unclear.