In an interview with ABC News, Loughner's former classmate and friend Tong Shan described him as a "good person that just somehow changed so much."
In 2007, Shan and Loughner had a class together at Pima Community College, and would sometimes would spend time together outside of school. After the semester ended, they fell out of touch. When Shan next saw Loughner, in the summer of 2010, she says he acted like a completely different person.
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"I don't know might have caused him to change, but from the way he was talking to me [online]... you can see. It was just questions and questions and random, weird questions that didn't go together," she said. "He would just trip out," she told ABC News. Shan described him as being 'anti-government' but said she never heard him talk about guns or violence.
Another student recalls Loughner's behavior at school as wildly inappropriate. According to the student, who took a poetry class with Loughner, Loughner made off-color statements after a girl read a poem about abortion, and mentioned terrorism.
A classmate of Loughner wrote in e-mails obtained by the Washington Post that he was a disturbed individual.
"We do have one student in the class who was disruptive today, I'm not certain yet if he was on drugs (as one person surmised) or disturbed. He scares me a bit," Lynda Sorenson, a 52-year-old wrote in an e-mail to friends on June 1. "Hopefully he will be out of class very soon, and not come back with an automatic weapon."
"We have a mentally unstable person in the class that scares the living crap out of me," Sorenson wrote in another e-mail on June 14. "He is one of those whose picture you see on the news, after he has come into class with an automatic weapon."
Loughner and his parents are loners who rarely spoke to their neighbors, those in the neighborhood told the Washington Post.
"You try to say something, they'd just ignore you and turn around and walk back into the house," Ron Johnson, a retiree who lives across the street from Loughner's home told the newspaper. "The kid - I never talked to him. He acted just like his parents and ignored you."
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Steven Woods, another neighbor of the Loughner family, said he hadn't had an interaction with them in the seven years they lived near one another.
Poems written by Loughner, obtained by ABC News, give a glimpse into the mind of the young man. In one poem, called "Meat Head," Loughner describes making eye contact with attractive girls whom he believed were waiting for their boyfriends. "Confused look on my face of no idea what to do, deciding to copy other men's routines..." he writes. In another poem, he describes a full moon setting at a cemetery.
Pima Community College sent a letter to his parents on Oct. 7 telling them that if Loughner wished to return to the school, he would have to "obtain a mental health clearance indicating that, in the opinion of a mental health professional, his presence at the College does not present a danger to himself or others," the school said in a statement.
Loughner was suspended after college police discovered a YouTube video apparently created by Loughner in which he claimed the college was "illegal," and he dropped out, the school told ABC in a statement.
Loughner attended a "Congress In Your Corner" event in 2007 and received a letter from Giffords thanking him for attending, according to an affidavit by an FBI agent.
Fox News reported on a law enforcement memo which states that there is "no direct connection" between Loughner and the extremist American Renaissance group. But, the memo states, "strong suspicion is being directed at AmRen / American Renaissance. Suspect is possibly linked to this group. (through videos posted on his MySpace and YouTube account.). The group's ideology is anti-government, anti-immigration, anti-ZOG (Zionist Occupational Government), anti-Semitic."
Loughner, Politico points out, seems to have been influenced by David Wynn Miller, a conspiracy theorist who believes, as Loughner wrote in one of his videos, that "the government is implying mind control and brainwash on the people by controlling grammar."
But Mark Potok of the Southern Poverty Law Center writes that it's "hard to say" if Loughner is a right-wing extremist.
"When you look at the Internet material he purportedly produced, the first impression you get is that the 22-year-old now in custody for the shooting of 19 people in Tucson was completely out of his mind, or at least mildly deranged," Potok writes. "His writings will be virtually impossible for most people to understand, what with his references to unexplained numbers, his fondness for weird syllogisms, his unexplained references and his apparent semi-literacy."
"At this early stage, I think Loughner is probably best described as a mentally ill or unstable person who was influenced by the rhetoric and demonizing propaganda around him," Potok writes. "Ideology may not explain why he allegedly killed, but it could help explain how he selected his target."
Additional reporting by Melissa Jeltsen.
Late Update: Nick Baumann of Mother Jones talked to Loughner's friend Bryce Tierney, who says Loughner left a voicemail message for him at 2 a.m. on Saturday. "Hey man, it's Jared. Me and you had good times. Peace out. Later," Loughner said in the message.