Get out there real early...buy a realistic Mckensie Decoy and setup in cover/brush to mask it. Run some mono fishing line to a tree branch near the head.

Get a video camera...wait for the guy...pull on the mono to look like a rubbing animal..and see if he shoots.

The GW's do this all the time. See if the GW will put out thier decoy?

OR...put up a dummy decoy surveillance camera aimed at his stand and tell him its a wireless continous feed to a computer recording his every move.