Dogs are domesticated animals and as such are only as good as their owners have trained them. Any dog that attacks or kills a human should find their owners responsible for any pending arrest or litigation against them. Dogs don't have civil rights in America whereas human beings do, so legally the humans are held responsible for the actions of pets or animals.
Yes. Dogs are sometimes victims of their own environment. Because they are pets, this environment is usually provided by their owner. The owner should be responsible for how their pet acts in public places. The easiest way to assure your dog will not attack or kill someone is to ensure there is plenty of love in the household.