Logic is anyone but Fredo. How is he going to kill two professional hitmen? Forget the "weak" part, and let's assume he was strong enough to do it. It would have required some degree of planning, so if you believed him when he said "I didn't know it was gonna be a hit" (as I do), then that excludes him as a possibility.
Anyway, we do have a lot of new members since the last time this question was raised. Maybe a new theory will emerge.
