He hustled to Walmart twice. He ran a red light, with the officer letting him off with a warning. Back home, he grabbed a black bag from the trunk of a family car and fled into the desert on foot, his suspicious father giving chase.
Later, Loughner took a cab to a Safeway supermarket and began squeezing off round after round into the crowd.
The new details of the Walmart visits and the traffic stop emerged Wednesday, adding to the picture of the last frenetic hours the 22-year-old spent before the attack Saturday that gravely wounded his apparent target, Rep. Gabrielle Giffords, and killed six others.
"It sounds like he was pretty busy that morning," Pima County sheriff's Capt. Chris Nanos said.
As Giffords' condition improved in an intensive care unit Wednesday, all federal judges in the state recused themselves from the case to avoid any future questions about their impartiality, given that one of their colleagues, John Roll, was killed in the rampage.
President Barack Obama flew to Arizona and met privately with Giffords and other victims still being treated at a hospital. Giffords opened her eyes for the first time since she was shot in the head shortly after Obama visited, the president said at a nighttime memorial service in Tucson.
At the memorial, the 14,000-seat University of Arizona basketball arena was filled, and another 13,000 people watched it on the scoreboard at the school's football stadium.
"Those who died here, those who saved lives here - they help me believe," Obama said. "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to us."
The new details about the way Loughner spent the morning showed a harried young man dashing from store to store across this southern Arizona city in the hours before the shooting that shocked the country.
Nanos said Loughner made two trips to Walmart and made some purchases. He declined to specify whether Loughner purchased ammunition.
At some point, an officer with the Arizona Game and Fish Department saw Loughner run a red light on a road that runs parallel to Interstate 10 around 7:30 a.m. and pulled over his 1960s dark gray Chevy Nova, authorities said.
The stop was about 6 miles from the Safeway store, agency spokesman Tom Cadden said.
Wildlife officers don't usually make traffic stops unless public safety is at risk, such as running a red light. The officer took his driver's license and vehicle registration information but found no outstanding warrants and let him go.
"All he saw were some fast food wrappers, no black bag," Cadden said. "The officer said he was polite and subdued."
Loughner had a valid license and insurance and the car was registered, agency spokesman Jim Paxon said. "He was warned and released because we had no probable cause to hold, or do an extensive search."
Sometime later, Loughner was back at his house on a block of low-slung homes with palm trees and cactus gardens.
Loughner removed a black bag from trunk of the family car. His father, Randy, saw him, and asked him what he was doing, said Rick Kastigar, chief of the department's investigations bureau.
Jared then ran off into the nearby desert, only to emerge later from a cab at the Safeway supermarket where Giffords was holding an event to listen to constituents' concerns, authorities said.
Hours after the attack, sheriff's deputies swarmed his home and removed what they describe as evidence he was targeting Giffords, including handwritten notes in a safe that read "I planned ahead," "My assassination" and "Giffords."
Among the notes was one with the words "Die, bitch," which authorities believe was a reference to Giffords.
Nanos said the writings were either in an envelope or on a form letter Giffords' office sent him in 2007 after he signed in at one of her "Congress on Your Corner" events - the same kind of gathering where the shooting occurred.
Investigators, however, are still searching for the black bag.
"What he did and the morning before the shooting, we're just trying to find all that out. Naturally, we want to find every detail we can," Nanos said, adding that Loughner may have made other stops that morning but could not specify what they were.
Later Wednesday, documents were released revealing details of the Loughner family's encounters with the Pima County Sheriff's Department and Jared's run-ins with police at Pima Community College in Tucson.
The college records detail Loughner's increasingly bizarre behavior last year, culminating with his suspension in September. The 51 pages of campus police reports, obtained under an open records request, described a series of classroom outbursts and confrontations that prompted worried instructors to summon campus officers.
Loughner's behavior grew from disruptive to deranged over time, but never violent, according to the reports. In one, dated Sept. 23, an officer called to quiet an outburst described Loughner as incomprehensible, his eyes jittery, his head awkwardly tilted.
"He very slowly began telling me in a low and mumbled voice that under the Constitution, which had been written on the wall for all to see, he had the right to his 'freedom of thought' and whatever he thought in his head he could also put on paper. ... His teacher 'must be required to accept it' as a passing grade," the officer wrote. "It was clear he was unable to fully understand his actions."
In a poetry class, he made comments about abortion, wars and killing people, then asked: "Why don't we just strap bombs to babies?"
Sheriff's reports detailed nine contacts officers had with Loughner or one of his parents, from May 1994 to March 2010. The first with Jared Loughner came in September 2004, when he reported that a fellow student pricked him with a needle.
In May 2006, police arrested Loughner on a misdemeanor charge of being a minor in possession of alcohol. He was taken from his high school to a hospital because he was drunk on vodka he had taken from his father's liquor cabinet.
"He advised he drank the alcohol because he was very upset as his father yelled at him," the report said. "I could see his eyes were very red and he was crying."
Loughner had a strained relationship with his parents, those who knew the family said.
In September 2007, Loughner was cited on a misdemeanor charge of drug possession after officers found two marijuana pipes, remnants of a joint and rolling papers in a van he was in with another teenage boy.
The officer who interviewed him reported that Loughner first denied having any contraband.
"I asked if I could search him. He said he had a right to say no," the officer wrote in a police report. But soon after, Loughner admitted to having a pipe in his pocket and apparently cooperated with the officer.
Jared Loughner has been charged with trying to assassinate the congresswoman, killing Roll and a 9-year-old girl, as well as fatally shooting a Giffords staffer. Judge Larry A. Burns in San Diego has been appointed to the case.
Giffords, who was shot in the head, is breathing on her own and responding non-verbally to doctors.
"We have really decreased the amount of sedation we are giving her and, as a result of that, she's becoming more and more spontaneous all the time," said Dr. Peter Rhee, trauma chief at the University of Arizona.
Associated Press writers Alicia Chang, Gillian Flaccus and Michael R. Blood in Tucson, and Jacques Billeaud and Bob Christie in Phoenix contributed to this report.