No "official" cause, perhaps, but there was a manslaughter trial against Williams and I'm sure there was some pretty compelling evidence introduced. Anyway, a documentary isn't supposed to be like the nightly news cast. The movie was an hour and 40 minutes long, they could have spent 5 minutes discussing it. I just think it was either sloppy film making, a poor editing decision, or conscious decision to not address that better than they did (i.e. fear of lawsuit).

It was a good movie other than that though, but that is the same thing as having a movie that is a murder mystery end by saying, "Gee, I guess we'll never know who killed that person. THE END." Kind of leaves you flat.