Charles Edward Pickett Jr. of Battle Creek was also charged with four counts of reckless driving causing serious impairment in the grisly accident Tuesday night in Cooper Township, north of Kalamazoo. Two of the victims remained in serious condition Thursday, and the two others were in fair condition, hospital officials told NBC News.
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If he's convicted, Pickett could face life in prison on the murder charges and five years apiece on the reckless driving counts.
Bond hasn't been set because Pickett is not yet "medically able" to attend an arraignment, Kalamazoo County Prosecuting Attorney Jeffrey S. Getting told reporters late Thursday afternoon, but he said prosecutors would seek to hold him without bond.
Getting wouldn't elaborate on Pickett's condition, citing medical privacy laws, and he wouldn't confirm or deny what he called "speculation" that the driver may have had drugs or alcohol in his system.
According to a complaint filed in Kalamazoo County District Court, prosecutors don't believe the deaths were premeditated, but Getting said the investigation is continuing as authorities try to figure out what led up to the crash.
The blue truck was seen swerving across several lanes for at least a half-hour before it plowed into the bicyclists, according to police.
"As members of the Kalamazoo community we have all been dealt a devastating blow by the deaths and injuries of so many innocent people," said Getting, who was expected to provide details at a news conference Thursday afternoon.
Alex Johnson is a reporter and editor for NBC News based in Los Angeles.