That is a threat and assault and you have a witness. I would call the sheriff RIGHT NOW and have him arrested. Plain and simple. When the sheriff shows up, show him your deed, have the rightaway clearly highlighted. Take the highroad on this one!!! Don't wait for something bad to happen to you. It's not your fault that he is a moron and didn't read his deed properly. The time for being neighborly is over, now go on the offensive.