I never really though about this one too in depth, because of the lighting in that scene, I just recently discovered who some of those guys actually were.Right after that scene,Mike is talking to Tom and he says, "Fredo and all his men" so maybe some of Fredo's men took care of the shooters, and then they were taken care of later, but that sounds a lot like a JFK theorey.Also I find it hard to believe that anyone could actually bring themselves to take orders from Fredo.Good question.