Mostly the subject of the photograph, which can be anyone really, coming down the street - someone that has no idea. "Heroism" in photography, just like in a novel, is for everyone.
There is an immense trout in Loch Awe in Scotland, which is so voracious, and swallows his own species with such avidity, that he has obtained the name 'Salmo Ferox'. I pull about this unnatural monster till he is tired, land him, and administer the coup de grace. Is this cruel? Cruelty should be made of sterner stuff.