Five bicyclists were killed and four others seriously injured when they were struck by a pickup truck Tuesday evening on a road in Cooper Township, Kalamazoo County Prosecutor Jeff Getting said.

In the half-hour before the bicyclists were struck, law enforcement in three jurisdictions received calls about a blue pickup truck driving erratically, Getting told reporters in a late-night news conference Tuesday night.

At 6:36 p.m., before officers could track down the truck, a blue Chevrolet pickup headed north on North Westnedge Avenue near G Avenue slammed into the group of nine riders as they climbed a hill near Kalamazoo County's Markin Glen Park. The truck became disabled after striking the bicyclists, and when police arrived, they found a man they believed to be the driver not far away on foot.

The man was arrested and remained in police custody Tuesday night.

The crash occurred on a tree-lined, two-lane stretch of North Westnedge Avenue, one of Kalamazoo's main streets as it climbs a hill out of the Kalamazoo River valley near the county's Markin Glen Park. The riders were northbound, riding on the right edge of the pavement, when they were struck from behind, Getting said.

"There is very little I can or will tell you about how exactly this accident happened," Getting said. He said not all families had been notified and he did not want facts about the scene reaching families through the news media.

"I can't even begin to imagine what they're going through," Getting said.

Watch the briefing (app users, tap here to watch):

Five people were pronounced dead at the scene. Two of the victims went to Bronson Methodist Hospital. They were listed in serious condition this morning, according to hospital spokeswoman Carolyn Wyllie. The other two were taken to Borgess Medical Center; one was in critical condition, the other was "fair," according to hospital spokesman Lew Tysman. Getting said news reports that children were part of the riding group were incorrect and that everyone in the group was injured.

Getting said Michigan State Police are in charge of the accident reconstruction effort that was ongoing overnight on North Westnedge; the Kalamazoo County Sheriff's Department will be in charge of the criminal investigation.

As calls about the erratic driving of the truck flowed into the Kalamazoo Department of Public Safety, the sheriff's department and the Kalamazoo Township Police Department, officers from each agency dispatched officers to try to find the truck.

"This was a moving target," Getting said.

The crash occurred before they found the truck, Getting said; he asserted that there was no pursuit in progress at the time of the crash.

Getting said he didn't expect a report from investigators before Thursday, when he will begin to determine what charges to file against the man.

The news conference less than five hours after the crash was held because "It was important to provide information sooner rather than later," Getting said. "From a public health standpoint, we wanted to put people's minds at ease" that there was not an ongoing risk.

"Police are on top of this," he said.

The prosecutor acknowledged that the mass-casualty incident, coming 3½ months after six people were killed in the Kalamazoo shootings, was hard on the community.

"I'm at a loss to describe how I feel about the impact to the community," Getting said, but he added that "I have every confidence in Kalamazoo and in Kalamazoo County and I know how the community will respond.

"I just wish we had had more of an opportunity to get our feet under us before we had to do it again."

Tuesday evening, the road was shut down and clogged with dozens of emergency vehicles. Concerned neighbors looked on in horror as word of the tragedy circulated.

Markus Eberhard said he often goes fishing at the location and was walking out of a store when "someone, I don't know who, told me watch out and I jumped back. The truck went past my foot – almost hit my foot, and I looked, and before I could tell the bikers to move, it was too late. I already heard a bunch of bikes hit his front end."

Gov. Rick Snyder issued a statement about the crash this morning.

"My thoughts and prayers are with the people of Kalamazoo and particularly the cyclists and their families," Snyder said. "The State Police were called to assist in the investigation and will continue to provide all the resources they can to help determine what exactly happened last night. What we already know for certain is that Michiganders as a family are in mourning today as Kalamazoo struggles to understand another senseless tragedy."

The Detroit Free Press and WZZM 13 contributed to this report.