Yes, and it usually is the fault of the owner. And pitbulls are like any other dog, without proper training, i.e., who is the Alpha, . . . there will always be problems.
I saw a news story a year or so ago where this lady answered the door, a policeman was knocking, and her five chihuahuas got out and attacked the officer, . . . no kidding, . . . he had quite a few stitches around his ankles if memory serves.