Holly Martins

How amoral can one become oneself without even knowing? Should friendship for one really be the overriding factor in our lives? A few moments ago on here (it could have been days) I shared the ending to The Third Man, and to claim that one of the main characters Holly Martins was actually left behind because he made the right, righteous choice. Now I read today that his character was a weakling who created an own world in which he could live therefore his choice to stop his friend (actually shoot him to stop him to get away) was wrong. Okay, shooting a friend isn't really a neat thing to do but he was faced with a decision not to let the person commit real evil any more. The friend was a baddie gone really bad. No morality there any more and such. Does anyone have the right to shoot at a friend then? Is that even still murder?