They didn't waste much time getting the body cremated, did they? There was a large party of Scientologists visiting the Bahamas with the Travoltas. I still believe it's possible someone from the church conked the kid on the head. They would have had their bases covered even if the kid lived. They could have then blamed his low level of mental functioning on a head injury. As he became an adult, the Kawasaki heart artery disease wouldn't have sufficed any longer as a cover. Remember, there are no brain disorders that can't be cured by the teachings of sci-fi comic book writer L.Ron Hubbard.