Anytime a dog attacks and kills a person the dog is at fault, the breed does not matter. There isn't any reason a dog should kill a person, especially a child. It doesn't matter what the child did the dog was at fault for killing the child.
If a dog attacks a person it is because the OWNER did something wrong. It could have been anything. Using agressive training tactics that made the dog fearful. Not properly socializing the dog. Owning a dog with known behavioral issues and not addressing them. Playing rough with the dog and teaching the dog it's ok to bite at people. Leaving a child alone with a dog. This list could go on and on and on...
Dogs are shaped by the enviornments they grow and live in. A dog does not suddenly decide "I don't like that son of a b****, I think I'll go kick his ass." There is always something more.
And by the way... I spend lots of time around GSD's, Pit bulls and other bully breeds, Rotties, etc.... I have been bitten by 2 dogs in my entire life. Ready? One was a Chihuahua and one was a Pomeranian. Go figure...