Gregg isn't talking, hasn't admitted to anything and what most people think it is or was is really inconsequential because he's deriving some kinda of pleasure from the attention that he gets, good or bad...why would he kill the golden goose, after all. I'm not going to buy his book to see if he admits to anything, however I will skim the pages at a Chapters for zilcho dolleros...but I still think he won't directly admit to exactly what he did, for whatever reason.
So I can safely say that the answer is: nobody knows. Case closed; the internetz is safe once again!