The Pittsburgh public safety department says the Pittsburgh officer was trying to help the unconscious man in the Sheraden neighborhood just before 12:30 a.m. Sunday.
Authorities said the Rottweiler bit the back of the officer's thigh, knocking him to the ground, and as he was getting up the animal "lunged at him again."
A public safety spokesman said the officer then shot and killed the dog, then was able to give medical attention to the owner before emergency medical personnel arrived.
The man was taken to Mercy Hospital in stable condition. The officer was also taken to a hospital for treatment.
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