This person sounds mentally unstable. Safest bet is to provide a statement to the police so they can put him on the radar as you may end up saving someone's life.
This guy is dangerous on the road. Sped up behind us and was beeping. We turned left and he decided to cut across the lanes so that he could pull up in front of our car, get out and confront us. Ended up another member of the public in the car also asking him to move on as he was blocking the road with his car. Totally unacceptable.
This person sounds mentally unstable. Safest bet is to provide a statement to the police so they can put him on the radar as you may end up saving someone's life.