BEVERLY HILLS, CA — "It's the gunshot that echoed around the world — but who pulled the trigger?"That's how the folks behind an upcoming documentary on the Kennedy assassination are hyping JFK: The Smoking Gun. The documentary premieres in November on the U.S. cable channel Reelz and on Discovery in Canada. Montreal-based Muse Entertainment — who produced the highly-rated 10-part miniseries The Kennedys — are also behind this venture.Executive producer Michael Prupas to