KALAMAZOO, Mich. — County officials say a shooter who killed six people and injured two others here Saturday was an Uber driver who appears to have gunned down people at random during a four-hour rampage.

Authorities said they are investigating reports that the suspect gave a harrowing ride to one passenger just 90 minutes before the shooting began and that he may have continued picking up fares during the spree of violence.

On Sunday morning, Kalamazoo County Prosecutor Jeffrey Getting said police identified the gunman as Jason Brian Dalton, 45, of Kalamazoo. Dalton was taken into custody hours earlier and appears to have acted alone. His victims, shot at three different locations, had no apparent relation to the assailant.

“These weren’t sudden explosions, this was done intentionally,” Getting told reporters during a briefing. “They appear to have been chosen at random.”

Four of the six victims killed were shot at a Cracker Barrel restaurant. State police identified them as Mary Jo Nye, 60, Dorothy Brown, 74, and Barbara Hawthorne, 68, all of Battle Creek, Michigan, and Mary Lou Nye, 63, of Baroda, Michigan.

Ninety minutes before his shooting spree began, Dalton picked up a Kalamazoo resident for an Uber ride, but drove so dangerously that the man cut the journey short and called 911. Another passenger said Dalton told her he had just started as an Uber driver a few days earlier and was already getting bad reviews. An Uber spokesman confirmed that Dalton was a driver for the mobile ride company.

Authorities said the rampage is not being investigated as an act of terrorism.

The suspect in Saturday’s shooting did not have a criminal record, police said.

“We are trying to piece together a motive,” Kalamazoo Public Safety Chief Jeff Hadley said Sunday. “Honestly, it appears to be completely and totally random.”

Getting said Dalton, who will be arraigned Monday, will likely be charged with six counts of murder, two counts of assault with attempt to commit murder, and six counts of committing a felony with a firearm. “And then we’ll see from there,” he said.

In speaking to reporters early Sunday, Getting said Dalton shot his first victim, a woman, multiple times outside the Meadow Townhomes complex at 6 p.m.

This woman, who was not identified, is “severely injured” but is expected to survive, Getting said. Paul Matyas, Kalamazoo County under sheriff, said the woman was with her three children at the time. The children appeared to be uninjured.

Four hours later, Dalton appeared outside the Seelye Automotive Group, a car dealership, at 10 p.m. and killed two men – an 18-year-old and an older man believed to be father and son – while they were sitting in their car.

Fifteen minutes after that, Dalton opened fire at a nearby Cracker Barrel restaurant, killing four people. A 14-year-old girl also was shot. Getting said she was “gravely injured” and it was unknown if she is expected to survive.

“This is your worst nightmare, where you have somebody just driving around randomly killing people,” Matyas told a local television station.

Getting said video from the car dealership and restaurant helped police identify Dalton’s car in the parking lot of a downtown bar where he was arrested at 12:30 a.m. without struggle. It was not immediately clear if he had been inside the bar.

A semi-automatic handgun was recovered from the car, Getting said, and a search of Dalton’s home produced evidence that suggested Dalton acted alone. It was not immediately clear whether Dalton had a license for the firearm, but neighbors said he was known to own several handguns.

An account from an Uber customer in Kalamazoo may provide clues to Dalton’s mental state on the day of the shooting. In a phone interview, Mackenzie Waite of Kalamazoo said her fiance was picked up by an Uber car around 4:30 p.m. for what was supposed to be a short ride costing $5. Halfway through the trip, the driver picked up a phone call on his bluetooth, Waite’s fiance later told her. Her fiance couldn’t hear what was said, but the driver began acting strangely.

“He blew through a stop sign, sideswiped a car, starting driving in (and) out of the other lane of traffic,” Waite said. “My fiance was just pleading with him to stop the entire time.”

When the car slowed down at one point, Waite’s fiance jumped out and immediately called 911.

Neighbors said there was nothing unusual about Dalton, who lived outside Kalamazoo with his wife and two teenage children. Neighbor James Bloch said his friend Dalton “must have flipped. He never was in that state of mind ever.”