A Michigan prosecutor filed murder charges on Thursday against the 50-year-old driver of a pickup truck that struck a group of bicyclists out for a casual ride, killing five of them and seriously injuring four others.

Kalamazoo County Prosecutor Jeffrey Getting charged Charles Pickett Jr. of Battle Creek with five counts of second-degree murder and four counts of reckless driving in the crash Tuesday in Cooper Township north of Kalamazoo.

Pickett is hospitalized and in police custody. He will be arraigned as soon as his health permits, Getting said during a Thursday afternoon news conference.

Getting cited patient privacy laws and declined to discuss why Pickett was hospitalized or his condition.

Police are continuing to gather information on what led to the crash and the charges were the first step in the legal process, he said.

He did not release details of what caused the crash, but said state police are analyzing evidence.

"There's been some speculation about, first, that he was drunk, second that there was something else in his system, third, now nothing at all is in his system," Getting said of Pickett. "I would encourage all of you to wait. Take a breath. All of this information will come out. This is a process that takes time."

Getting added that he will wait on reports from state police crime lab "before I tell anyone what was or was not in his system at the time."

Often, in suspected drunken driving cases, blood samples of the drivers are taken for testing to determine how much — if any — alcohol is in that person's system.

The bicyclists ranged in age from 40 to 74. They were five miles into a weekly 30-mile ride when they were struck from behind near a park.

Police said they had received complaints about a pickup being driven erratically and were searching for it minutes before the crash on the two-lane road.

The driver fled on foot but was caught by police shortly afterward.

"I know some of the specifics about where he was, where he came from," Getting said of Pickett. "I can't go into specifics on that."

If convicted of second-degree murder, Pickett could face up to life in prison.

The bicyclists were part of a group that called themselves "The Chain Gang."

Mark Rose, who co-founded The Chain Gang about 15 years ago, said its members weren't "hardcore," but biked regularly for the exercise, enjoyment of being with friends and the "safety in numbers." He said he dropped out several years ago to focus on running.

"They were just casual cyclists who enjoyed the ride," said Rose, 58, of Galesburg.

Killed in the crash were Debra Bradley, 53, Melissa Fevig-Hughes, 42, Fred Nelson, 73, Lorenz Paulik, 74, and Suzanne Sippel, 56. The injured bicyclists were Paul Gobble, 47, Sheila Jeske, 53, Jennifer Johnson, 40, and Paul Runnels, 65.

Bronson Methodist Hospital in Kalamazoo reported that Jeske was upgraded to fair condition from serious. Runnels remained in serious condition at that hospital.

Gobble was in serious condition and Johnson was in fair condition at Borgess Medical Center in Kalamazoo.