THE PILOT MADE A DISTRESS CALL, GIVING HIS POSITION AND SAYING THAT HE WAS 'GOING IN.' THE WEATHER WAS VFR. THE AIRPLANE STRUCK A 5600 FT MOUNTAIN AT THE 5530 FT LEVEL IN A WINGS LEVEL ATTITUDE. IMPACT OCCURRED ON A STEEP ROCK WALLED AREA OF THE MOUNTAIN AT HIGH SPEED. THE ENGINE CONTROLS WERE POSITIONED FOR POWERED FLIGHT. THE PILOT LEFT HIS AUTOBIOGRAPHY, MEDICAL HISTORY, AND HIS WIFE'S DEATH CERTIFICATE IN HIS PARKED CAR. THE PILOT'S MEDICAL HISTORY INDICATED HIS DEPRESSION OVER THE RECENT DEATH OF HIS WIFE & HIS CONCERN ABOUT DETERIORATING HEALTH. THE PILOT'S SON SAID HIS FATHER PLANNED TO COMMIT SUICIDE IN HIS AIRPLANE. A DEATH CERTIFICATE, ISSUED BY THE COUNTY CORONER, LISTED THE PILOT'S DEATH AS A 'SUICIDE.' TOXICOLOGY TEST RESULTS FROM THE PILOT'S LIVER & KIDNEY TISSUE INDICATED THE PRESENCE OF FLUOXETINE, WHICH IS AN INGREDIENT OF PROZAC (PRODUCT NAME), A PRESCRIPTION ANTIDEPRESSANT MEDICATION.