Any animal provoked or trapped in a bad spot will bite no matter how good the family dog was mine has done that his self because it didn't want to be bothered. All dogs will bark its there instint to bark, other if trained and teased by prob casued the dog to bite will be bad. I have never been around a pit bull that was nice then turned against people. If a dog is teased then it will looked at its teaser as enemy's. If you want a dog to nice and loyal then don't tease or mistreat it or it will turn against its owner.