De Pere police say the death of a man in his 50s is being treated as suspicious.  The dead man’s name hasn’t been released yet.  His body was found Thursday on the shore of the Fox River in De Pere.  A coroner estimates he was in the water for about 12 hours.  Officers say they know the man from his prior run-ins with law enforcement.  No self-inflicted wounds were found and there was a sizeable police presence along the river trail early Thursday evening while the crime scene technicians looked for evidence.