Two young boys were being watched by their grandparents. Neighbors say the grandparents were inside the home napping when one boy went missing.
Neighbor Joann Zaborowski saw all the commotion when police arrived to the home.
"Horrifying, I could not imagine," she said.
Police say the child apparently wandered into the family's unlocked car. Saturday's high temperature reached about 86 degrees.
It is not known how long the boy was inside the car.
Some neighbors say they don't understand how this could happen.
"How would he get into the car without being watched," said neighbor Eric McNamee "Even if grandpa and grandma were taking a nap there should have been some arrangement where someone was watching them, you cannot let a child that young out of your sight."
The boy was transported to Oakwood Heritage Hospital and pronounced dead.
Romulus police are investigating the death and an autopsy is scheduled to be performed.