Let everyone have a gun
Quick background check to purchase and carry
Quick background check to purchase, but more difficult to carry
Background check, waiting period for purchase and carrying.
Background check, waiting period, no carrying
No guns at all
One good citizen did more than community agencies. Loughner was turned away from buying ammo from one Wal Mart because the guy at the gun counter said Loughner was acting strange. That's rather significant considering how difficult it would be to single one person out in a Wal Mart as exhibiting strange behavior. That Wal Mart refused to sell him bullets. Kudos to them.
The systems (laws, procedures and policies) that should have identified Loughner failed. The NICS did NOT fail. Loughner's behavior at Pima Community College was so bazaar that the school declared him persona non grata as it feared he would be a danger to himself and others. The US Army refused Loughner's enlistment because Loughner informed them he was addicted to pot. When Sportsman's Warehouse ran Loungher's ATF 4473 it came back clear. It shouldn't have.
"When Faith preaches Hate, Blessed are the Doubters." - Amin Maalouf