KALAMAZOO, Mich. — As details emerge about the night authorities say Jason Dalton has admitted gunning down six randomly chosen victims in and around Kalamazoo — attacks apparently carried out over hours during which he also ferried passengers around town as an Uber driver — any hint as to why remains stubbornly elusive.

A prosecutor said Monday that Dalton picked up fares for the ride-hailing service after the first shooting Saturday that left a woman seriously wounded and probably got more riders after the two subsequent shootings that proved fatal. But none of the shootings appeared to be connected to fares. Uber officials acknowledged the company received complaints about Dalton’s erratic driving that day, and said that company policy is to contact the driver when alerted to unsafe driving. But they would not say whether anyone at the company spoke to Dalton.

Dalton, meanwhile, appeared briefly in court by video link and was charged with six counts of murder, which carry a mandatory life sentence. A judge denied bail for the 45-year-old former insurance adjuster, who Kalamazoo police Det. Cory Ghiringhelli told the court had admitted to investigators “that he took people’s lives.”

The admission seemed only to deepen the mystery of what was behind the killings of six people with no apparent connection to the gunman. Police and prosecutors acknowledge a motive may never be fully known.

“This is a terrible moment in the community. We face violence like any other community does but nothing on this scale,” said Kalamazoo County prosecutor Jeff Getting. “We’ve lost six people, we have a 14-year-old girl clinging to life, we have another victim who is recovering, thankfully, … we have a high school that’s lost a classmate.

“And no one understands why it happened.”

An Uber passenger said he called police to report that Dalton was driving erratically more than an hour before the shootings began.

Matt Mellen told Kalamazoo television station WWMT that he hailed a ride around 4:30 p.m. Saturday. He said Dalton introduced himself as “Me-Me” and had a dog in the backseat.

Mellen sat in front. About a mile into the trip, Dalton got a phone call, and when he hung up, he began driving recklessly, blowing through stop signs and sideswiping cars, Mellen said.

“We were driving through medians, driving through the lawn, speeding along, and when we came to a stop, I jumped out of the car and ran away,” Mellen said. He said he called police and that when he got to his friend’s house, his fiancée posted a warning to friends on Facebook.