The Pima County sheriff's office on Friday says an extended clip was found nearby and Jared Loughner had two more 15-round magazines in his pockets, though it doesn't say if any of those were loaded.
Authorities say he used a Glock semiautomatic handgun with an extended clip that held 33 bullets in the attempted assassination of Rep. Gabrielle Giffords.
The sheriff's office says a deputy found the gun on the ground.
Loughner was arrested after the attack that wounded 19 people, six fatally.
Also in his pockets were a 4-inch buck knife, a plastic bag with money, a Visa card and his Arizona driver's license.
On Thursday, a man walking his dog hasholding ammunition that authorities believe Loughner discarded during a frenetic morning in which he fought with his father, ran away on foot, , and ultimately attempted to assassinate Rep. Gabrielle Giffords.
Authorities have said the suspect, Jared Loughner, and his father got into a confrontation over the bag at their home in the hours before the shooting.
This detail is the latest in a series of snapshots emerging about the final hours before Loughner allegedly opened fire with a semi-automatic Glock handgun in a crowded Tucson Safeway parking lot.
Authorities said Wednesday that a wildlife officer pulled over the suspect in the assassination attempt against an Arizona congresswoman less than three hours before the deadly attack.
Lougher, 22, ran a red light but was let off with a warning at 7:30 a.m. Saturday, the Arizona Game and Fish Department said. The officer took Loughner's driver's license and vehicle registration information but found no outstanding warrants on Loughner or his vehicle.
The night before the shooting, Friday, Jan. 7, Loughner slept at an area motel. He apparently drove to the motel in the Chevy Nova now parked at the Loughner home. Police have since searched the vehicle thoroughly.
At 2:33 a.m. Saturday, Loughner visited a convenience store less than a mile from his house, CBS News reports. Alone, he bought a doughnut, a soft drink and several energy bars. He did not buy alcohol.
Surveillance video of Loughner at the Catalina Mart has been given to the FBI, which wanted the video to see if he had any accomplices, CBS News reports. The FBI scanned Loughner's credit card purchases to track his whereabouts before the shooting.
The morning of the shooting, Loughner went to two WalMart stores to buy ammunition. He left the first store because the clerk was too slow. He bought the ammo at the second store.
Either right before or right after buying the ammo, Loughner was pulled over for running a red light and released, in the earlier described incident.
After being pulled over, Loughner went home and had a confrontation with his father, Randy Loughner.
Loughner, who was chasing his son after seeing him remove a black bag from the trunk of a family car, said Rick Kastigar, chief of the Pima County Sheriffs Department's investigations bureau. Randy Loughner had apparently asked after the bag, and his son then fled.
After the run-in with his dad, he took a cab from a convenience store to the Safeway.