TUCSON, Ariz. — In the hours before the assassination attempt against Rep. Gabrielle Giffords, Jared Loughner went to Walmart, was pulled over for running a red light and ran from his father after an angry confrontation.

Investigators now are piecing together the timeline of Loughner’s frenzied morning before the attack that killed six.

“What he did and the morning before the shooting, we’re just trying to find all that out,” said sheriff’s Capt. Chris Nanos.

Nanos wouldn’t say what Loughner bought during two trips to Walmart.

After the shopping trips, Loughner ran a red light but was let off with a warning, the Arizona Game and Fish Department said. The officer took Loughner’s driver’s license and vehicle registration information at 7:30 a.m. but found no outstanding warrants and didn’t search the car, a late 1960s dark gray Chevy Nova.

About 8 a.m., Randy Loughner saw his son walk to one of the family’s vehicles and take a black bag out of the trunk.

“The father went out and said, ‘What’s that?’ and he mumbled something and took off running,” said Sheriff Clarence Dupnik.

Randy Loughner got in his truck and chased his son, but Jared ran into the desert.

At 10:11 a.m., police say Jared Loughner showed up at a Tucson grocery store in a taxi and shot 19 people, killing a federal judge and a 9-year-old girl, among others and wounding more than a dozen.