I am going to write it down. I will have to think a lot and come to an agreement with my partner before I can decide to talk non-anonymously to the authorities.
You can talk anonymously to the authorities. They may not be able to do much but at least they can keep an eye on the guy. There is an organization called the Office of Special Investigations. They handle this kind of stuff. Letting them know the activity exists might be enough to get them to open an investigation and watch the guy.
I do appreciate your advice on this.