According to Port St. Lucie police, as officers responded to reports of a dog locked in a 2003 silver Mercury Sable "circling the cul-de-sac while in the reverse gear."
Investigators learned the car owner made a wrong turn on his way home, said Senior Sgt. Lisa Marie Carrasquillo, police spokeswoman.
The driver got out and shut the door, leaving the dog inside.
"The dog named Max accidentally hit the shifter into reverse, causing the car to circle the cul-de-sac, leaving the owner locked out of the car," police stated. "As the car circled the cul-de-sac, it struck and damaged a mailbox."
Carrasquillo said Max apparently was driving for several minutes.
Carrasquillo said the driver provided an extra key fob, but the battery was dead.
Police wound up entering the code on the key pad of the door.
"The dog is happy and fine," Carrasquillo said Friday.
Max, who apparently wasn't wearing a seatbelt, did not get a citation.
There were no injuries reported.