For what its worth, a very knowlegeable poster on another forum had stumbled upon an FBI file that stated that Gerlando Sciascia was believed (by the Bonanno admin) to have ordered the murder of Cotroni's son and was killed himself as a result of it. I'm not sure, but I believe this was apparantly said by Massino himself.

"It was between the brothers Kay -- I had nothing to do with it."