A North Texas man says his dog had to be euthanized after being hit by a rock allegedly thrown by a mail carrier.

Fort Worth police and the U.S. Postal Service are investigating what happened to a Yorkshire terrier named Maxwell. Postal officials issued a statement saying the carrier was defending himself from a dog attack.

Owner Lawrence Brown says his pet on Saturday apparently wandered across the street. Brown later heard howling and found the injured animal. Brown says he saw the mail carrier, asked what happened and the postman said he hit the dog with a rock.

Brown says Maxwell had a skull fracture and spinal injuries. The dog was euthanized.

Fort Worth police say nobody has been charged.

The name of the postal carrier hasn't been released.