We had one of those too, but after reaching the state you describe at the end, my company actually sued him for harassment after a while, which shut that down (at least for us, those people tend to just switch targets). We also had 2 stalkers over the years, one of them was describing what people were wearing, making clear that he had line of sight into the call center (it was in a very low density area with a wide view, someone with a good telescope could have been miles away) - in this case the police was involved immediately and they hired a security guard for the night shift. I have many complaints about my former employers, but this at least was handled the way it should be.
We had one of those too, but after reaching the state you describe at the end, my company actually sued him for harassment after a while, which shut that down (at least for us, those people tend to just switch targets). We also had 2 stalkers over the years, one of them was describing what people were wearing, making clear that he had line of sight into the call center (it was in a very low density area with a wide view, someone with a good telescope could have been miles away) - in this case the police was involved immediately and they hired a security guard for the night shift. I have many complaints about my former employers, but this at least was handled the way it should be.