KALAMAZOO, Mich. (Reuters) - The Michigan Uber driver charged with murdering six people switched vehicles after sideswiping a car at the start of the shooting spree, authorities said on Tuesday, adding they hoped his phone would help establish a motive for the killings.

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It was also disclosed that the suspect, Jason Dalton, who was reported to have obtained a community college degree in law enforcement two decades ago, visited a gun shop shortly before the shootings and bought a heavy-duty jacket that could conceal a small pistol.

Dalton, 45, was denied bail on Monday after a court hearing in which a detective testified that he admitted to the five-hour shooting rampage over the weekend in Kalamazoo, Michigan, about 150 miles (240 km) west of Detroit.

Hours before the first shooting occurred on Saturday evening, Dalton and a friend visited Southwick’s, a gun shop he frequented in nearby Plainwell, a shop employee told Reuters.

Dalton was a regular customer who usually spent time chatting with the staff, but he bought the jacket and left the store within 10 minutes, said the employee, who asked not to be identified.

“He’s in here enough for me to know he talks to the guys about guns and different stuff,” she said.

Searching for a motive behind the violence, investigators focused on a 9mm semi-automatic handgun and a cellphone seized from Dalton, as well as the fact that he picked up fares for the Uber car-hailing service between or after the shooting episodes, authorities said.

At least one passenger who rode in Dalton’s car that night, apparently after the rampage had begun, recounted that the Uber driver seemed oddly calm and even appeared to be fatigued to the point of almost falling asleep at the wheel.

“He didn’t say much and he didn’t act abnormal. He was rather quiet,” Marc Dunton, 39, told Reuters of the ride he shared with two friends, taking the front-passenger seat beside Dalton.

Prosecutors say Dalton randomly shot at people at an apartment complex, a car dealership and a restaurant, killing six and badly wounding two others, including a 14-year-old girl left in critical condition.

“Right after the first shooting at the apartments, he left the scene and sideswiped a car,” said Paul Matyas of the Kalamazoo County Sheriff’s Department. The accident prompted him to switch cars, from a silver Chevrolet Equinox to a Chevy HHR, both vehicles belonging to his family, Matyas said.

Dunton said he was picked up in an HHR. Another Uber passenger, Matthew Mellen, told CNN he rode in Dalton’s Equinox and that Dalton seemed normal until he received a call on his cellphone, at which point he began driving erratically, running stoplights and a stop sign and sideswiping another vehicle.

Matyas said investigators were examining Dalton’s Uber contacts and working to “track his phone calls, track his whereabouts” in the hours before his arrest early on Sunday.

Detroit-based NBC affiliate WDIV-TV reported that Dalton graduated from Kalamazoo Valley Community College in 1992 with an associate’s degree in law enforcement and criminal justice but did not enroll at the school’s police academy.

He had no criminal record, authorities said.