I agree, that is exactly what he was doing. I would have at least called the law on him and had them waiting at his truck when he got back. He now knows that you probably won't do anything, somost likelyhe'll be back. That was the perfect opportunity to have the law catch him "in the act". Would have been even better if he had a weapon, which it sounds like he didn't. Someone else around you is hunting...he's part of that group.