Without seeing the deer, it would be hard to say!
Legality, and ethics, USUALLY go hand-in-hand, BUT SOMETIMES THEY DON'T!
In a "suffering" situation, I would take the law into my own hands, others might choose to follow the "letter of the law!"
Personally, I would just have to deal with the consequences, if the Wardens saw it differently than I did!
In ANY case, I'd say that the best that you can do, would be to follow your heart! Or, as DD would say, "to thine own self be true!"