A Michigan man who worked as an Uber driver is due to be arraigned on Monday in the fatal weekend shootings of six people in Kalamazoo as police search for a motive in a case that raised questions about how the car service vets its drivers.

Jason Dalton, 45, faces 16 charges, including six of murder, which can bring up to life in prison, the county's prosecutor said. An initial records search indicated Dalton had no criminal record and no known links to extremist groups.

Prosecutors alleged Dalton randomly shot multiple times at people during a five-hour period on Saturday at an apartment complex, a car dealership and a Cracker Barrel restaurant in Kalamazoo, about 150 miles west of Detroit.

RELATED: Kalamazoo shooter accused of killing six to be arraigned in Michigan

Police were investigating reports Dalton also may have driven customers of the Uber car-hailing service the night of the rampage. Two people were wounded in the shooting, including a teenage girl who was initially thought to have died. No motive has been given.

"The Kalamazoo community is reeling from these senseless acts of violence that took so many innocent lives from us," said Jeffrey Getting, the county's prosecuting attorney.

Initial checks with a key federal agency and the Southern Poverty Law Center indicate Dalton was unknown to both law enforcement and counter-terrorism agencies for having any kind of known connection to extremist groups.

"This guy had no criminal history," Kalamazoo Police Chief Jeff Hadley told CNN on Monday. "There is a lot we don't know right now."

An Uber  representative confirmed Dalton was a company driver and had passed background checks.

The attack renewed interest in how the company screens drivers, who use their personal vehicles to ferry customers at prices generally below those of established taxi companies. Critics say the company never meets potential drivers in person.

Getting said on Sunday the victims apparently were chosen at random and shot multiple times.

RELATED: Michigan Uber driver shoots and kills six people while on duty

Michigan State Police said the shooting began at about 5:30 p.m. with the report of a woman wounded outside an apartment building. At about 10 p.m., a father and son were killed at the car dealership.

Dalton allegedly opened fire outside the restaurant about 15 minutes later, killing four women identified as Mary Lou Nye, 62, of Baroda, Michigan; and Dorothy Brown, 74; Barbara Hawthorne, 68; and Mary Jo Nye, 60, all of Battle Creek, Michigan, state police said.

He was arrested without incident while driving away from the parking lot.

The Detroit Free Press said neighbors described Dalton as a father of two who "loved guns," worked on cars and had a day job as an insurance salesman.

Uber passenger Matt Mellen said he got into a car with a man who was probably Dalton about an hour before the shootings started and taken on a terrifying trip.

"We were driving through medians, driving through the lawn, speeding along and when we came to a stop, I jumped out the car and ran away," Mellen told local TV broadcaster WMMT.