It could have been a postal inspector. They are plain clothed and are federal law enforcement agents with the authorty to arrest. I would think he would have shown a badge or federal ID.Originally Posted by c6h6o3
Postal employees are instructed to inform either the postal police or the inspectors if there is suspicious activity on or in federal property. They should not act on their own.
It is too bad, it looks like a very nice building to photograph.