I agree with Pottsy. I would first show the note to my neighbor. Then I would go to the Game Warden and County Sheriff. I think it is a fair assumption that you have been left a potentially threatening note from a person armed with a high powered rifle. I doubt seriously that the hunter left the note when he wasn't hunting. I would tell each of them that I no longer felt safe while working on my land. If the Owner, Game Warden and Sheriff will talk to the guy, I expect he will move his deer stand.
I would definately have a couple of game cameras. However, the effective distance is seldom over 50 ft. They do make binoculars that incorporate a digital camera. I think I would watch the guy. If he starts scoping onto your land, take a picture. Show it to the authorities. Under no circumstances does he have the right to look onto your land with a loaded deer rifle.
By the way, a friend of mine was ticketed for "stalking" deer. He watched some big bucks on a game farm for about 10 minutes through the scope of his loaded rifle. The Game Warden ticketed him and admitted in court that he knew that my friend had no intention of shooting a deer. However "letter of the law" caused my friend to lose the case. It's a fairly new Texas law that Game Wardens can use against road hunters that don't actually fire a shot.
