Medina told investigating officers that he felt his vehicle "go over a bump," which he at first thought was just a speed bump in front of his duplex in the 600 block of West Wilson Street, according to a statement from the Police Department.
It wasn't until Medina heard neighbors screaming that he stopped to see what was going on, police said in a report.
The boy was taken to a local hospital, where he was pronounced dead on arrival due to massive head injuries, said Sgt. Phil Meyers.
Police have determined that neither drugs nor alcohol played a part in the accident. The investigation is ongoing.
"It's a tragedy no matter which way you slice it," Meyers said.
Meyers said "skilled investigators in the field" determined that fatality was the result of an accident.
"But we still have to review the reports and review the coroner's report and a whole myriad of issues before the case is closed," he added. "On its face, it appears to be an accident, but we still have to dot the I's and cross the T's and look into it thoroughly."
Meyers said the Medina family also has a 4-year-old, who was inside the pickup with his father at the time of the accident.