"Jason Brian Dalton had passed a background check, and was a driver-partner with Uber," said Uber's chief security officer, Joe Sullivan, in a statement. "We have reached out to the police to help with their investigation in any way that we can."
While the company did not address reports that Dalton picked up and dropped off customers Saturday night, authorities told CNN that it was "certainly part of our investigation."
"We're looking into his connection to Uber and whether or not he was picking up fares in between the shootings," said Public Safety Chief Jeff Hadley.
Kalamazoo County prosecutor Jeff Getting said the first shooting took place around 6 p.m., when a woman was shot four times in an apartment complex parking lot. Getting said the woman -- who was with her three children -- is in serious condition, but expected to survive.
Jason Brian Dalton was arrested in connection with a shooting rampage.
Then, four hours later, two men -- an 18-year-old and an older male -- were shot and killed at a Kia dealership. Hadley said the pair were there looking at a vehicle. Getting, who would not identify any of the victims, would not confirm reports that it was a father and son.
Ten minutes after that, at around 10:10, police say Dalton fired on two vehicles in the parking lot of a Cracker Barrel restaurant, killing four adult women and "gravely" injuring a 14-year-old girl. Getting said authorities initially thought the teen was dead. "Call it a miracle," he said. "But she's alive now."
The prosecutor said the Cracker Barrel victims were together in a single group.
After another two hours or so, at approximately 12:30 a.m., police took Dalton, 45, into custody, ending a six-hour nightmare that brought Kalamazoo to its knees.
Police seized a semiautomatic handgun from Dalton, whom Getting described as "even-tempered" at the time of his arrest.
"There is just no question more people would have died if (police) didn't find him when they did," Getting said.
Motive unknown
The cruel randomness of the rampage seemed to rattle officials in the western Michigan city.
"This is your worst nightmare," Kalamazoo County Undersheriff Paul Matyas told CNN affiliate WOOD-TV. "When you have somebody just driving around randomly killing people."
"We just can't figure out the motive," said Hadley. "There's nothing that gives us any indication as to why he would do this or what would have triggered this. The victims did not know him, he did not know the victims."
Getting appeared to struggle at times for the right words, if there were any, at Sunday's press conference.
"There is this sense of loss, anger, (and) fear," he said. " On top of that, how do you tell the families of these victims that they were not targeted for any other reason than they were a target?"
Getting said he was confident that Dalton acted alone, and that there is no connection to terrorism. Formal charges will be brought Monday, he said.
"I would expect six counts of murder, two counts of assault with intent to commit murder, six counts of felony firearm, and then we'll see from there."
'Typical American family'
For the last ten years, Sally and Gary Pardo have lived across the street from Dalton's single-family home on Douglas Street in Kalamazoo.
Sally Pardo told CNN that Dalton is married with two children, and that they seemed to be a "typical American family."
"This seems so out of sorts for him," said husband Gary Pardo, who described Dalton as "quiet" and "nice."
He did tell CNN, however, "I know he liked guns."
Getting said he didn't know if Dalton had a license for the handgun that was seized at the time of his arrest.
CNN's Ryan Young, Brad Parks, Nick Valencia, Joe Sutton and Vivian Kuo contributed to this report.
