crazy guy

Sean Penn went ballistic on a paparazzo this afternoon -- and we've learned the photog just filed a police report against the actor.

The cameraman -- Jordan Dawes (not a TMZ guy) -- is accusing Penn of battery after a confrontation near the Brentwood Country Mart in Los Angeles, where Sean had just eaten lunch.

Penn was seen kicking and hitting the photographer on a side-street multiple times before leaving.

Sean's rep had no comment.