The only person inside the vehicle at the time was their neighbors' 2-year-old girl.
The boy's father is suing Nicholas and Laura Kruse, accusing them of negligence.
"You can only protect them so much, your 20 feet away he's riding on the sidewalk, you can only protect him so much that one split second," said Johnny Bergman, father.
The lawsuit asks for a judgment of more than $2 million.
Nicholas and Laura Kruse did not want to comment.
Police say Laura Kruse told them the car was off and in park when she left it.
