Mail Box Thief in the Neighborhood???

I was walking down Prospect Place between Vanderbilt and Carlton at 5:20 this morning and I notice a guy on the other side of the street. (At that hour you notice everybody.) I watched as he went stoop to stoop checking mailboxes for whatever. When he noticed me he stopped and started playing with his phone. Didn't actually see him take anything, so don't feel I can call him a thief, but can't imagine why else he was doing it. Make sure you bring your mail in every day. (Didn't have my phone with me so couldn't call police, and of course, can never find a cop when you need one.)