I kinda wanted to put in my two cents on this. I think that Alcatraz wallows in his guilt over that one single action. He has this image of what a hero is that includes someone perfect, someone who would gladly give themselves up for someone else. When he failed some of his internal criteria, he mentally assigned the label "Not a hero" and since everybody viewed him as one anyways, he decided he was a terrible person, since he knew he wasn't the person they thought he was. But when it came down to it, he did try very hard to succeed in doing the right thing. He failed (or at least it seems like he did), which he added into the label of "Not a hero." I don't think he meets the expectations he sets for himself to be a hero, but I think that he qualifies anyways. Heroes are allowed to make mistakes.