Lucchese and Olivant: I admit it's a big stretch to imagine Fredo as the killer of the Tahoe gunmen. And I qualified it by saying that I was guessing. But I offer two rejoinders:

First, FFC and Puzo made Fredo almost a cartoonishly dumb character. But a silver lining in our perception of his terminal simplicity is that we were all the more shocked when he turned out to be the traitor. No matter what his role, he was pivotal to an assassination plot that very nearly worked.

Second, none of us, including me, has ever definitively answered the question of who killed the Tahoe shooters. This is one attempt. If there's a better theory, let's hear it (again).