Well, y'know, had Luck been the one to discover what was happening, he would have killed those three as he did the vampires.
As for the behavior of police officers in the US, the primary problem is the doctrine of Qualified Immunity, invented by the US Supreme Court over the years from 1967 through 1982. From the 1870s until 1967, there was no legal question that police officers were personally responsible for any violation of someone's rights. Since 1982, unless precedent establishes rather specifically that an officer could not act in a particular way, he or she is indemnified against criminal and civil action.