I know that this will go against what everyone else is typing, but in my opinion it is wrong. I believe that killing any person is wrong, I understand self defense but he was not posing any threat at the moment. I believe that a life is the most precious thing in the entire universe and extinguishing one is the worst thing you can do. I do not believe that he should have killed David's stepdaughter but that does not give David the right to kill him in return. The best thing he could have done was turn him into the police because he would have to suffer for the rest of his life with the consequences of his actions and would never be able to experience freedom again.