The twisted frame of a sport-utility vehicle was all that was left after Saturday night's crash.
"It appeared that the car had flipped four times, with the one person being ejected -- a 4-year-old child being ejected," Michigan State Police Tpr. Chris Grace said in an interview Sunday evening.
Grace is investigating the crash. He says the four-year-old boy may not have been restrained.
"(His) mom says he often times would take his own belt off. So, don't know if he was belted in, my guess is no," Grace said.
The 4-year-old, his 10-year-old sister and his 25-year-old mother -- all from Taylor in Wayne County -- were hurt.
A 24-year-old woman from the Wayne County city of Gibraltar was killed. Her 7-year-old son survived.
The two families were returning to the Detroit area from a cheerleading compeition in Grand Rapids when the crash occured, just east of Fowlerville along I-96 in Livingston County's Handy Township.
Now, investigators are saying what they believe caused the fatal accident.
"Although the cars didn't have any contact between them, yes, the car did cause the Explorer to roll over," Grace said.
The car the trooper is referring to was driven by a 56-year-old Ingham County man. State police investigators believe that driver cut off the SUV. They also think they know why that happened.
"The driver was distracted by an insect that had gotten inside of his shirt and he was trying to get that insect from his shirt," Grace said.
Now, charges could be filed against the 56-year-old.
And they could come soon. State police investigators will turn over the results of their investigation to the Livingston County prosecuting attorney Monday.
Two of the four injured in the crash were treated and released Saturday night.
As of Sunday night, the four-year-old thrown from the SUV was still in critical condition. His mother was still in stable condition. Both were receiving treatment at the University of Michigan Medical Center.