Back to the original post/question.

Had I been in your situation I can honestly say I would have left the animal alone. You keep talking about the guy who owns the trap. You apparently know him? Well, you saw he had trapped an animal, being a hunter yourself, your first instinct should have been to go let the gentleman know so that he could dispose of the animal however he wished.

I can understand how you felt though and I'm not saying you did the wrong thing, I would have just handled it differently.