Bad fences worse neighbors

I purchased an acreage over 20 years ago. The back of the development was cut into several large tracts, mine was 26 acres. Just before closing, the seller hacked back a small chunk in the back corner for fear that it would land lock another parcel since the road made a turn. That parcel sold soon after, and was split between two guys who then built houses.
Not long after, one approached me about being allowed to graze a couple of horses on my land, and I said OK, if they put up the fences at no cost to me. They built the fences, but did not follow the property line very well. The stakes had disappeared, but I knew roughly where the lines were.
A few years later, I cut my chunk up into five lots. four five acre ones, and a six acre on the corner. Not long after, I sold two of the tracts which included the fence the neighbor had built for horses.
The guy who built on the end tract and the one who built the fence got along just fine. Both had an interest in old cars so they visited a bit and never any issues. Well, the guy who had the horses liked to drink. He went through a divorce, remarried, and managed to take a bad fall. He died soon after, and his estate sat in probate for well over two years while his children and ex-wife shredded his new wife over the property.
The property sold last week, finally, and it looks like we are about to get the neighbor that they make Investigation Discovery shows about. They had a survey done, the pins were located, and the new stakes are in to mark the boundaries. The new guy then proceeded to come on to the neighbors property and cut trees, and is telling him he is going to remove the fence which sits on the land I once owned. The drive way also encroaches on the land, so that is going to be an issue real fast. Mark, the guy who put it in, insisted it was all on his place back when he built. I had issue with it, but never spent the $2,000 to get a new survey. It did not matter, adverse possession would never be an issue.
I read a lot on the ag forums. Plenty of assholes in the world. Oh well, I've got a good camera and plenty of SDS cards.