(CNN) Authorities charged accused Kalamazoo, Michigan, shooter Jason Brian Dalton on Monday with six counts of murder, two counts of assault with intent to commit murder and eight firearms violations.

He showed no emotion in court as the charges against him were read. A judge denied Dalton bail.

For nearly five hours Saturday, police say, the shooter drove from one target to another, gunning down victims at random.

And in between the shootings, he apparently picked up passengers for Uber.

As families mourn the deaths of six people in Kalamazoo County, one question looms above all else: Why did the gunman do this?

Here's what we know and don't know about the attacks:

The shootings

What we know:

The gunman shot eight people in three different parts of the county Saturday evening, authorities said.

Kalamazoo shootings

Around 5:42 p.m., he shot a woman in front of her children at an apartment complex parking lot, prosecutor Jeffrey Getting said. The woman was struck multiple times but is expected to survive.

Four hours later, the gunman killed a father and son at a car dealership, police said.

Minutes afterward, he drove to a Cracker Barrel restaurant and opened fire in the parking lot, killing four women and wounding a 14-year-old girl.

Two of the shootings were captured on video, Getting told CNN on Sunday.

"These were very deliberate killings. This wasn't hurried in any way, shape or form," said Getting, who has reviewed the video with police.

"They were intentional, deliberate and I don't want to say casually done. Coldly done is what I want to say."

What we don't know:

How the gunman chose the victims.

"There isn't a connection that we've been able to establish between any of the three victim groups with each other, any of the three victim groups with the defendant," Getting told CNN's "New Day" on Monday. "It just is, well, it was random, unprovoked violence."

Kalamazoo County Undersheriff Paul Matyas called it "your worst nightmare" in an interview with CNN affiliate WOOD-TV in Grand Rapids.

The seemingly random selection of victims makes the rampage even more difficult to cope with, said Kalamazoo Public Safety Chief Jeff Hadley.

"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?"

The suspect

What we know:

Two hours after the final shooting, police arrested Dalton, 45, without incident in downtown Kalamazoo. Police also seized a weapon from his car.

The gun, a semi-automatic pistol, according to Getting, seems to match shell casings at the three shooting scenes, he said.

Jason Brian Dalton was arrested in the Kalamazoo shooting rampage.

Dalton was driving for Uber the night of the shootings and even picked up and dropped off passengers between attacks, a source with knowledge of the investigation told CNN.

Matt Mellen told CNN affiliate WWMT-TV he rode in Dalton's car just before the shootings started.

"We got about a mile from my house, and he got a telephone call. After that call, he started driving erratically, running stop signs," Mellen told the station.

WOOD-TV reported that another man told the station he had sought an Uber ride as a safer alternative to walking with a killer on the loose, only to end up, apparently, in Dalton's car.

"I kind of jokingly said to the driver, 'You're not the shooter, are you?' He gave me some sort of a 'no' response ... shook his head," the station quoted the man, whom it identified only as Derek, as saying.

"I said, 'Are you sure?' And he said, 'No, I'm not, I'm just tired.' And we proceeded to have a pretty normal conversation after that."

Uber's chief security officer told CNN that Dalton passed a background check. Police also said Dalton did not have a criminal record.

"For all intents and purposes, he was your average Joe," the public safety chief said. "This was random."

What we don't know:

Who that phone call was from when Dalton was driving Mellen, and whether the call may have played any role.

The victims

What we know:

The names of the victims.

Authorities named the first victim as Tiana Carruthers, who was shot in front of her children before 6 p.m. Saturday.

Tyler Smith, 17, was killed along with his father Saturday night.

Next were Richard Smith, 53, and his son Tyler, 17, who were looking at a vehicle at a car dealership when both were shot and killed, police said.

Tyler's girlfriend, also 17, witnessed the shootings from the back seat of their car, according to Hadley, the Kalamazoo public safety director.

"The suspect got out of his car. Walked up to them, shot them and then left," Hadley said. "Coldblooded."

The last shooting happened in the parking lot of a Cracker Barrel restaurant. Authorities say four women were killed as they sat in two cars: Dorothy Brown, 74; Barbara Hawthorne, 68; Mary Lou Nye, 62; and Mary Jo Nye, 60.

A 14-year-old girl who was in the passenger seat of one of the vehicles was also struck. Her family identified her Monday as Abigail Kopf.

Hadley said Sunday the girl was in "very, very critical condition." A day later, he said the girl is "still holding on" and responding to verbal commands.

"She's our bright light," he said.

What we don't know:

How many more victims might have been killed if police didn't catch the suspect.

"There is just no question more people would have died if (police) didn't find him when they did," said Getting, the prosecutor.

The motive

What we know:

Police say they don't think the shootings were acts of terrorism.

Four women were killed in the parking lot of this Cracker Barrel restaurant.

Under federal law, terrorism refers to a violent or dangerous crime that appears to be intended to either (1) intimidate or coerce a civilian population; (2) influence government policy by intimidation or coercion; or (3) affect government conduct by mass destruction, assassination or kidnapping, constitutional lawyer Page Pate wrote

"My best sense is that it was somebody who was having an issue at the time and for whatever reason they decided to do what they did," Kalamazoo County Sheriff Richard Fuller told CNN's "New Day" on Monday.

What we don't know:

Virtually everything else about the motive.

"That's always a difficult thing to try and figure out when you're dealing with these random acts of violence," Getting said Monday.

While Dalton was known to like guns, "there wasn't anything that would put him on the police's radar as someone who would be likely to do to something like this," he said.

Some of those answers could be coming, however. At a probable cause hearing just before an arraignment, detectives testified that Dalton said he told them that he "took people's lives," after he was read his rights that include the right to remain silent.

Fuller told CNN on Monday that Dalton is cooperating with investigators.