The boy's parents took him to the hospital Sunday saying he'd been left in a hot car, von Lutcken said.
He died on Wednesday.
An autopsy was done to determine the child's exact cause of death.
The child was left in the car for about an hour and a half before being discovered by the parents, according to the Florence County Sheriff's Office.
Coroner von Lutcken said he is waiting on more test results before he rules on the manner of the baby's death.
The case is under investigation by the Coroner's Office and the Sheriff's Office.