In another video posted on YouTube, Loughner uses repetitive, convoluted logic when defining terrorism.
"If I define terrorist then a terrorist is a person who employs terror or terrorism, especially as a political weapon. I define terrorist. Thus, a terrorist is a person who employs terror or terrorism, especially as a political weapon," the video, entitled "Introduction: Jared Loughner," says. "If you call me a terrorist then the argument to call me a terrorist is Ad hominem. You call me a terrorist. Thus, the argument to call me a terrorist is Ad hominem."
In the YouTube profile, the account holder, identified as Loughner, lists "The Communist Manifesto" and "Mein Kampf" among his favorite books.
Laughner's Myspace page features a picture of a handgun on a U.S. history textbook. A senior military official told ABC News Loughner attempted to join the Army but "never made it past the urinalysis."
A high school classmate of Loughner's said he was extremely political in high school, but not radical. The classmate said Loughner once met Giffords in 2007 and said he thought the congresswoman was "unintelligent."
Police are still on the hunt for another man they said may have been involved in the shooting.
ABC News' Elisa Roupenian and Emily Friedman contributed to this report.