Since the local police came and checked him out, I bet he is an LEO on a surveillance. He could be parked a block away from the spot he is watching. Or, his partner might have "the eye" and he is sitting back several blocks away waiting for something to happen.
I used to be the head of a surveillance team and that is how we did it. I remember one time when my partner had the eye and I parked in an apartment complex a couple of blocks away to eat my lunch and read a book. Someone there called the police on me. They came, checked me out, and went away again.
Or, you all could be right and he is up to no good. Not likely, though, IMO, since he has been sitting there so long. Surveillance is often long and boring.
