My cousin's daughter and her friend were mauled by 4 pit bulls out in the country. They ran through a field to try to escape to her house, which wasn't far away, but the pit bulls caught them.
It tore her scalp almost completely off and she had huge chunks of flesh torn from her arms and legs. She barely lived. If some women hadn't driven her car across the field to help, she would have been dead. And this is a road that has very, very, very little traffic. It was truly a miracle this woman showed up when she was needed.
I've heard how gentle and calm these dogs can be, and I believe the people when they say their pets are like that. But I wouldn't trust one of them a bit to remain like that if circumstances set them off. They're bred to kill.