You seem fixated with Pit Bull stories...
What's up?
If you look, you can find scores of stories about police dogs biting innocent bystanders. These people sustain serious injuries in most cases.
Statistics report over 4 million people are bitten by dogs in a given year. Given that information, and the press' love of hysteria, you can see how it's easy to come up with a stream of "PIT BULL BITES (fill in the blank)!!!!" articles.
Sad to say, there are people in this country who want "bad" dogs. Their idea of a good dog is one who will bite a person they (the owners) don't like. Currently, the "pit bull" is their favorite type of dog, followed closely by the Rottweiler.
Dog experts know that irresponsibility, coupled with the above desire for a "bad" dog, is a recipe for trouble.
Nine times out of 10, a dog involved in a biting incident is off leash, on or off his owner's property. The dog is twice as likely to be an unneutered male, and to have had no training whatsoever, and little if any Veterinary care.