That's why I preface my Rocco theory as it being just a theory with no foundations other than it cleans up the mess of the assassins nice and neat. In lieu of any other reasonable explanation, it's certainly no different than supposing that Fredo or Fredo's men killed the assassins which I find far less believable.

However, since there's only reference to ONE traitor, i have to just let my Rocco theory remain on the back burner.