to deal with my neighbors, at least initially. I think you can still have a very frank conversation that starts with asking for an explanation of what purpose he had in being back there without starting by telling him you called the police and are notifying the neighborhood watch and contacting everyone on NextDoor. Are you 100% positive there is no set of circumstances under which you'd be less concerned than other circumstances?

I would ask him the question, see how you feel about his response, with the plan that almost anything he says is going to be met with your response, which would be along the lines of "Be that as it may, I'm not comfortable with you doing what you did. I'm sure you saw some of my cameras but probably didn't see all of them. I don't want this to become a problem, and if this happens again I won't hesitate to contact the police."

That way, not only does he know that you have cameras, but he knows that you saw him and that you recognize him.