While this may sound farfetched at first, Woody Harrelson's father WAS a hitman, and is currently serving a life sentence for murdering a federal judge with a high powered rifle.
Hmmmm... I'll bet THAT helped Woody Harrelson along in his career, since the mob has always controlled Hollywood.
BTW - That book is about Sam Giancana and the mob. There's lots of Kennedy dirt in it, but it doesn't get to the assasination of Marilyn Monroe or the Kennedy bros until towards the end. Good stuff!