Police say another car hit Kohlmeier's squad car, which was stopped in the I-55 median turnaround just north of Route 23. The driver of the other car is hospitalized, but his or her condition is not known.
Police say it was raining at the time of the crash, but it isn't clear if weather played a role. At this time, they're not saying if the driver who struck Kohlmeier's squad will face charges.
"Our investigators are conducting interviews with witnesses and we are working with the Livingston County State's Attorney's Office. No further information will be available until our investigation is complete," Lt. Steve Riesenberg said.
Flags at the Pontiac Police Department were lowered to half-mast.
"Casey was a 6 year veteran with Pontiac police department and a veteran of the United States Air Force. Officer Kohlmeier left behind his loving parents, his family and a whole community of friends," Police Chief Jim Woolford, Pontiac Police Department, said.
In 2009, Kohlmeier and his dog Draco found Tracy Pitchford's 2-year-old daughter when she got lost in a corn maze.
"I had so much gratitude, so much respect for him. If it wasn't for him, we may have never found her," Pitchford said. "Casey was a great person. He had a great personality. He was just very kind, and so many people loved and adored him."
Chief Woolford said Kohlmeier was part of the Livingston County Pro-Active Unit, which is made up of several area police departments, and hoped to join the FBI.
"It's a hole that we're not prepared to fill right now. It means a lot to us. There's not an officer in this country that doesn't regard Casey as a beloved friend so, we're deeply wounded," Chief Woolford said.
Funeral services for Kohlmeier were scheduled Saturday. Visitation was set to start at 8 a.m. at Pontiac Township High School with the funeral to follow at 12 p.m.