TUCSON, Ariz. -- Jared L. Loughner had trouble with the law, was rejected by the Army after failing a drug test and was considered so mentally unstable that he was banned from his college campus, where officials considered him a threat to other students and faculty.
But the 22-year-old had no trouble buying the Glock semiautomatic handgun that authorities say he used in the Tucson rampage Saturday that left six dead and 14 wounded, including Arizona Rep. Gabrielle Giffords.
Loughner's personal history did not disqualify him under federal rules, and Arizona doesn't regulate gun sales. His criminal charges were ultimately dismissed, the Army information was private and Pima Community College isn't saying whether it shared its concerns about Loughner with anyone besides his parents.
Loughner cleared a federal background check and bought the handgun at a big-box sports store near his home Nov. 30 -- two months after he was suspended by the college. He customized the weapon with an extended ammunition clip that would have been illegal six years earlier.
There is nothing to indicate that anything went wrong in the process leading up to that purchase -- except the ultimate outcome. But the question hangs: Was there any single piece of behavior -- or a combination of two or more -- that might have prevented Loughner from obtaining the gun that police say he used during his rampage?
Background checks are designed in part to weed out prospective gun buyers who have felony criminal records, have a history of domestic violence or are in the country illegally. None of that applied to Loughner.
There were warning signs, but nothing in his past that should have disqualified him under the laws and regulations as they are written today.
Gun-control advocates say the shooting shows that Arizona, home of some of the nation's most permissive gun laws, must review its laws to make sure firearms are not falling into the wrong hands. Gun rights proponents disagree and say more regulation would not have stopped the tragedy.
Arizona eased gun restrictions last year when it passed a law allowing residents 21 and older to conceal and carry a weapon without a permit, which allowed Loughner to furtively -- and legally -- carry his pistol to the mall where he is accused of opening fire.
No permits or licenses are required at the state level. Legal gun owners can bring concealed weapons into Arizona bars and restaurants, and state legislators are considering allowing students and teachers to have weapons in schools.
After the shooting, Pima County Sheriff Clarence Dupnik berated Republican lawmakers who have sought to further ease state gun laws.
"I think we're the Tombstone of the United States of America," the Democrat said, referring to the Wild West town populated by gunslingers.
Charles Heller, co-founder and secretary of an Arizona group that promotes gun rights, said more regulation is not a solution.
"Why don't we ban murder? Murders are illegal and people do it anyway," he said. "There is no way to weed people out."
In October 2007, Loughner was cited in Pima County for possession of drug paraphernalia. But the charge was dismissed. Loughner was arrested in October 2008 on a vandalism charge near Tucson but that case was also dismissed.
Last year, college police were called in five times to deal with Loughner's classroom and library disruptions.
He was suspended from the college and a college spokesman did not respond to an e-mail asking if the college had referred any information on Loughner to local police.
Critics have faulted Arizona for the availability of guns. A report released in September by Mayors Against Illegal Guns, an association of more than 500 mayors, found that nearly half of the guns that crossed state lines and were used in crimes in 2009 were sold in just 10 states, including Arizona.