This is why pitt bulls are banned in a lot of counties (such as mine). I don't necessarily agree with a ban on any breed of dog. A responsible dog owner does not allow his dog to get out and attack either another dog or humans.
My neighbor's pitt bull gets under the fence; he is a force to be reckoned with. They know it and they have made minimal effort to correct it. They refuse to watch the dog when he is outside. Three nights ago, their pitt bull got out (he very easily slips under their fence) and attacked me and my defenseless 14-year-old dog. My dog was on a leash and no where near their yard. The attack was without provocation of any kind and my dog was unable to defend herself against this brute. Hearing my screams, the owners came outside, but had no control whatsoever over their untrained dog. Only by throwing things at him could they get him back in their yard.
Maybe I do agree with bans; but, not on dogs - on irresponsible humans! My dog was lucky to escape - she is injured and horrified, but, fortunately, it wasn't worse.