The subject has been observed in every major city on earth, usually at the exact moment something happened, usually pretending to look at a crumb.

He wears the coat because it has pockets and nobody asks about it. He carries the folder because it makes people assume he is on his way somewhere. He is not on his way somewhere. He is where things are, and he was there first.

What is in the folder has not been confirmed. What is known is that every time somebody says 'nobody saw that', there was a pigeon.