Lenexa ? Investigators have been piecing together evidence in the fiery five-vehicle accident on Interstate 435 that killed three people.

Police said Kenneth C. Harris, 22, of Overland Park was killed when his northbound van crossed the median into the southbound lanes. The van driven by Harris struck two other vans head-on, triggering the five-car accident about 11:30 a.m. Saturday.

Investigators were looking into reports that Harris had a medical condition that could have contributed to the crash. But police haven’t ruled out other possibilities and have been developing timelines of what each driver was doing 24 hours before the accident.

“It’ll determine if anyone was tired or had been drinking or complaining of feeling ill,” said Highway Patrol Lt. Tom Catania.

John A. Hilkenkamp, 52, of Fenton, Mo., was killed when his southbound van was struck by the van driven by Harris. Hilkenkamp’s wife and son were injured in the accident. The family was in town for a youth soccer tournament.

Janet K. McNamara, 58, of Lee’s Summit, Mo., was killed when Harris’s van hit her van. She was alone in the vehicle and had just finished presiding over a funeral as an ordained minister.

McNamara’s van was pushed into a car driven by a Spring Hill woman who was injured in the wreck.

A fifth car was damaged by debris. All three vans burst into flames.

Trooper Greg Peters said Harris was on his way to work as a security guard.

Peters said Harris had a history of seizures but was taking medication over the past year and had no reported seizures during that time.

“So we don’t know if that contributed or not,” Peters said. “We’re hoping the autopsy report will tell us everything we need to know.”

Witnesses told Kansas Highway Patrol troopers the man was slumped over the steering wheel seconds before he passed through the grassy median, which does not have a guard rail or steel barrier to separate the northbound and southbound lanes.