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.
Classmates from Mountain View High School in Marana, a Tucson suburb, saw a different side of Loughner. They described him as intense and intelligent, someone who kept to himself but was nice once you to know him. He was fixated on numbers and excelled at math, former girlfriend Ashley Figueroa told CNN affiliate KGUN.
"He was a very nice kid. He was very, very intelligent. He would help me out with like my math and that's how it started off," Figueroa told KGUN.
"He just seemed like one of those kids who kind of kept to himself. He was very, very quiet. I kind of made the effort to talk to him because he kind of kept to himself. He was actually a really nice kid when it came to it," added Figueroa.
But his temper was too much for Figueroa, so she ended their relationship, she said.
"He used to scare me sometimes and that's why I left him. He kind of made me feel uncomfortable at times," she said. "He'd get really mad, clench his fist and then throw a kind of little tantrum. He'd flail his arms and walk off."
Loughner dropped out of Mountain View in 2006, after his junior year, the school district said. Near the end of his junior year, Loughner was taken to a hospital for alcohol poisoning, according to Sheriff's Department records. In 2007, he was arrested for possession of drug paraphernalia, but the charge was dismissed after he completed a pretrial diversion program, according to court records.
In 2008, Loughner tried to enlist in the U.S. Army but was rejected for reasons that are protected by privacy laws, officials said. But an administration official told CNN on Sunday that Loughner had failed a drug test.
Loughner had most recently been taking classes at Aztec Middle College, a partnership between Tucson schools and Pima Community College that helps dropouts transition to community colleges.
Loughner took classes until September 2010, when he was suspended after five contacts with Aztec campus police "for classroom and library disruptions" between February and September, the school said.
To his college classmates, Loughner's presence was unnerving, drawing the attention of campus law enforcement.
"The first time I was really struck by him was because he used inappropriate reactions to people's emotional content. He would laugh at things that were sad. He just didn't seem to be aware of what was going on," Don Coorough, his classmate in advanced poetry, told CNN.
A report on Loughner's participation in the poetry class noted an instance of him responding inappropriately to a poem read in the class.
His comments "were a huge leap from the context of the poem and said things about abortion, wars, killing people, and 'why don't we just strap bombs to babies,' " according to a February report by the Pima College Department of Public Safety.
Loughner was kicked out of an algebra class in June after repeated interruptions that made classmates uncomfortable and left the impression that he clearly "needed psychological help," his algebra instructor Ben McGahee said.
Loughner sometimes shook, blurted things out in class and appeared to be under the influence of drugs at times, McGahee said.
"I was scared of what he could do," McGahee said.
"I wasn't scared of him physically, but I was scared of him bringing a weapon to class."
Loughner was suspended in September after authorities found a YouTube video in which he called the school "illegal according to the U.S. Constitution," the school said.
A follow-up letter warned that in order to return, Loughner had to present a doctor's note stating that "his presence at the college does not present a danger to himself or others."
Off campus, Loughner got into trouble with police for underage drinking and possession of a marijuana joint and a pipe. Pima County Sheriff's Bureau Chief Richard Kastigar described them as "very minor" incidents that failed to raise red flags ahead of Saturday's extreme violence.
"[They] do not add up in their totality to anything that would cause a police officer to say, 'This guy is going to go out there and shoot 20 people,'" Kastigar said.
Immediately after the shootings, law enforcement and the media went online to decipher Loughners digital footprint. They found a trove of confounding items in his profiles on MySpace, YouTube and other sites. Creating his own currency, lucid dreaming and distrust of the U.S. government were recurring themes in his online writings.
A December 30 posting states: "Dear Reader ... I'm searching. Today! With every concern, my shot is now ready for aim. The hunt, a mighty thought of mine."
One posting complained of a "second constitution," a term legal scholars sometimes use to describe post-Civil War amendments that ended slavery, extended voting rights and required equal protection under the law.
"In conclusion, reading the second United States constitution I can't trust the current government because of the ratifications: the government is implying mind control and brainwash on the people by controlling grammar," he wrote in a December 15 video message on YouTube. "No! I won't pay debt with a currency that's not backed by gold and silver! No! I won't trust in God!"
Alan Lipman, director of the Center of the Study of Violence at Georgetown University, said the postings show "classic signs of psychosis."
"People were looking for whether he was on the left or the right. He was neither," Lipman told CNN. "He was incoherent. Those were signs, classic signs you'd see in a psychiatric unit of formal thought disorder."
Forensic psychologist Kathy Seifert called the postings "absolutely psychotic." Loughner should have been evaluated for schizophrenia, bipolar disorder, autism or other mental illnesses, she said.
In an apparent reference to Giffords' congressional district, a posting stated: "The majority of people, who reside in District-8 are illiterate - hilarious."
The last message reportedly posted on his MySpace page read, "Dear friends ... Please don't be mad at me. The literacy rate is below 5%. I haven't talked to one person who is literate."
Authorities believe Loughner specifically targeted Giffords. Searches of the Loughner home turned up a 2007 letter from Giffords thanking Loughner for attending a 2007 event similar to Saturday's, Kastigar said.
Other alleged connections to Giffords: an envelope in a strongbox in his home was scrawled with phrases like "die bitch" and "assassination plans have been made," though officials have not drawn a direct link to Giffords.
Neighbor Steven Woods said Randy Loughner had complained to another neighbor that his son was "out of control."
The morning of the shooting, Loughner and his father had a confrontation in their front yard, Kastigar said. His father had asked him about a black bag he was carrying.
"Jared mumbled something back to his dad, and his dad said he didn't understand what was said. It was unintelligible," Kastigar said. "And then Jared left. The father followed. The father got in his vehicle and tried to locate his son and followed the direction that he went and he could not locate his son."