Investigators say they are baffled. Neighbors are totally bewildered. All around this traumatized city, residents wonder whether they will ever learn why Jason Brian Dalton allegedly gunned down random strangers while picking up fares for Uber.

This week, as police continued looking for clues into Saturday’s shootings, so did people close to him. One neighbor was puzzled to learn Dalton, 45, was driving for Uber and not working for Progressive Insurance anymore.

“He left every morning at 8 a.m. like he was going to work,” the neighbor said.

Where he was going, what he was enduring, what he was thinking — mass-shooting experts say all these fragments will eventually coalesce into a motive that probably made perfect sense to the killer, even it’s incomprehensible to everyone else.

Crosses with the names of victims of a shooting spree rest by the side of a tree outside a Cracker Barrel in Kalamazoo this week. (Chelsea Purgahn/Kalamazoo Gazette-MLive via AP)

“In these cases, people typically don’t just snap and go berserk,” said James Alan Fox, a Northeastern University criminologist and author of several books on mass murders. “It may seem senseless, but there’s always a reason.”

For investigators, sorting that out takes time. For everyone else, the waiting is agonizing, a cruel ritual in the age of mass shootings. So far, all investigators have been able to offer is Dalton’s statement that “he took people’s lives.”

“This first thing I thought of was, why?” said Kalamazoo resident Lisa Stavish, 33. “Everyone I know is talking about it, but no one really knows anything.”

In some mass shootings, the reason is almost immediately apparent.

A married couple in San Bernardino, Calif., stockpiled bombs and ammunition for a shooting motivated by radical Islamist beliefs. In Colorado, a religious drifter with bitter beliefs about abortion is charged with killing three people at a Planned Parenthood clinic. Dylann Roof, who had expressed his hatred of African Americans, stands accused of killing nine of them in a Charleston, S.C., church.

But most mass shootings aren’t that simple to unravel. Experts say they typically combine precipitating events that might seem like everyday problems — work, money, love — with undiagnosed or untreated mental health issues. Sometimes the idea for a mass shooting unfolds over months. Other times, it’s days.

“It’s not something he did spontaneously,” Fox said.

In many ways, Dalton fits the typical profile of a mass shooter — a white male with no criminal record, no psychological impairment known to those around him, and the ability to legally purchase firearms.

What makes him different, Fox said, is that he “killed people in the wrong place at the wrong time.” Meaning he targeted total strangers without a specific setting.

Most mass killers, even if they target strangers, single out specific places for attacks. Students pick schools. Disgruntled workers pick their workplaces. Those making political statements choose symbolically important places.

Dalton’s setting was the entire city of Kalamazoo, making his motive more difficult to piece together.

J. Reid Meloy, a psychiatry professor at the University of California at San Diego who studies mass murderers, said investigators typically find “a mental state that is coming apart” and recent stressors causing difficultly in life.

“We think there’s an event that starts the clock,” he said. “But the predisposition to commit a mass murder has often been there for quite some time.”

What may have been Dalton’s event?

Working for Uber, as Dalton had been since late last month, is a clue that might indicate he needed extra money or that he couldn’t find a regular job. If he had a grudge against Uber, killing strangers while picking up fares could make total sense to him. But there’s also a danger in being too reductive.

Meloy said mass killers are often in a depressed and paranoid state, though there’s usually a kernel of truth that they feed on. While stressing that he was not talking specifically about Dalton, Meloy said that in cases appearing to take place randomly, “the individual has placed victims into a pseudo community.”

Uber was something he apparently kept from those around him, including the neighbor, James Bloch. They often talked about politics, guns and other current events through their backyard fence. As far as he knew, Dalton was still working for Progressive, including driving a company van.

“Probably around seven months ago he stopped driving it,” Bloch said. “And I asked him what was up with it — they said they were downsizing and they weren’t using the company vehicle anymore, that he had to use his own vehicle.”

In recent weeks, Bloch noticed that Dalton would return home at odd times: 11 a.m., 3 p.m. “He never came home at the same time,” Bloch said. “It was always different.”

Was he depressed? Bloch said no. Did he seem mad about something? Bloch said no.

One of the riders Dalton picked up said he began driving erratically after getting a phone call. But it is not known whom the call was from and whether it somehow set him off.

Even if a motive is not readily apparent yet, Fox said, “clearly something was going on making him miserable and unhappy. And if he’s miserable and unhappy, then other people need to suffer, too.”

To Fox and other experts, it seems clear Dalton was quietly planning something. A local gun-store owner said Dalton came in Saturday, the day of the killings, to buy a vest for concealing handguns. And then there’s his alleged steely demeanor during the attacks, still picking up customers and reportedly switching vehicles.

“That reflects the calmness that is typical in mass killers,” Fox said, noting that many mass killers are seen smiling while shooting. “Because they plan their crime, if only in their head, it’s something comfortable to them. So they are calm and cool and the rest of us are totally caught by surprise.”

One characteristic Dalton does not share with other mass killers: He’s still alive.

Most mass shooters kill themselves or are killed by police. That leaves open the possibility that Dalton will eventually explain his actions to authorities or a court-appointed psychiatrist.

So far, he’s mum on that topic.

“From what detectives told me, he is unaffected, kind of monotone,” said Kalamazoo Police Chief Jeff Hadley. “Showed no emotion relative to the offense. It’s really just baffling.”

Rosenwald reported from Washington.