He had fairly severe emotional issues....bi-polar or manic depression among them and was known to have a very hard time handling the fame.
IIRC, the coroner had ruled it accidental. They found no drugs in his system (he had dried out and went drug free), and they found that part of the ground at the end the cliff that had given way from underneath his feet. He had also just gotten engaged and had signed a multi-million dollar movie deal (as a producer).