I'm not trying to speak for my7pt but I think it might be the case that he justisn't able to get across with words how he feels. I think I know how he feels because I feel and feltit too...

The last buck I ever shot with my rifle was 4 seasons ago when I started bowhunting. After I shot it, I walked over to it and thought to myself, WOW I got about one tenth the rushthat I get with the bow. At that moment I didn't so much feel ashamed but I certainly wasn't anywhere near as proud of that buck as ones I've shot in the past. And at that moment, I sorta felt as if I'd done the buck and thus the creator wrong because I took a life that I wasn't more proud of. That was the year I decided I wouldn't ever shoot another buck with my rifle.

I think that is what the author means about the "shame" he felt.