The thing about deathbed confessions is -- you don't always know when you're going to die.  We've had no deathbed confessions from any potential Zodiac Killers yet either.  Maybe Zodiac isn't dead yet.  Then again, maybe the conspirators with the Kennedy assassination aren't dead yet either.  (I suspct Zodiac is Robert Graysmith.  But that's another conspiracy).  Jack The Ripper didn't confess to our knowledge either.   Furthermore, a deathbed confession may have happened, and nobody is willing to come forward that they heard it.  Then you have people who get Alzheimers, and are unable to give any deathbed confessions.  

 

Even if Oswald shot him, I don't see why he had to work alone.  

---