Loughner was also arrested when he was a teenager for marijuana possession.
And once enrolled at Pima Community College, Loughner was investigated five times by campus police.
In February 2010, police interviewed Loughner after a teacher referred to him as "creepy" and as having a "dark personality" after he allegedly suggested that a girl who had written a poem about an abortion strap a bomb to the baby.
The campus officer eventually determined that the incident did not "justify making contact with Loughner by police," according to the report.
A few months later, a teacher called campus police after Loughner grew "very hostile" upon learning that his grade in his pilates class was a "B." According to the report the teacher felt "intimidated" and had concern that Loughner might turn physical, requesting that an officer "be nearby" on the last day of class. Campus police monitored the classroom, but never spoke to Loughner about the complaint, the report says.
Over time, Loughner's behavior appeared to become stranger.
In September, after Loughner disrupted a math class, an officer who questioned the suspect about the incident wrote, "Loughner's head was constantly tilted to the left and his eyes were jittery."
The next week, when officers went to tell Loughner that he had been suspended from Pima after violating the student code of conduct for taping a YouTube video on campus during which he declared the college unconstitutional, the 22-year-old held a constant trance of staring at the school official.
The official wrote in a report that Loughner stared at him for an hour as the official spoke to the student and his father. When Loughner did finally speak, he said, "I realize now that this is all a scam."
Information gathered during Pima College's investigation was never shared with the Pima County Sheriff's Department, according Bureau Chief R.J. Kastigar.
"It came to light during the investigation [into Saturday's shooting]," said Kastigar.
The sequence of events the morning of the shooting is also become clearer.
At 5 a.m. Loughner posted a message on his MySpace page, writing, "Goodbye friends...don't be mad at me."
Then his attempt to buy ammunition at a Wal-Mart is rejected because the salesman found his behavior to be "erratic," but Loughner is successful buying the clips at a different Wal-Mart.
At 7:30 a.m., Loughner runs a red light and is pulled over by an Arizona Game and Fish Department officer. The officer found no outstanding warrants and let Loughner go with a verbal warning to drive carefully.
Just a half hour later, Loughner's father Randy spots him pulling a black bag from the trunk of their car.
"His dad asks him and he mumbles something back to dad that's unintelligible, as what the dad has told us. And then he turns around and he leaves," said Kastigar. "His dad follows him and attempts unsuccessfully to find him."
Less than two hours later Loughner takes a taxi to Rep. Gabrielle Giffords event, one she tweeted about at 9:58 a.m.
Thirteen minutes later, Loughner was allegedly firing.
Loughner faces five federal charges: one count of attempted assassination of a member of Congress, two counts of killing an employee of the United States and two counts of intent to kill employees of the United States. He will likely face state charges as well.
He is currently being held at the Phoenix Correctional Institution, 140 miles north of Tucson, where sources say he is sitting in his cell, smiling.