The official report states 'death by misadventure' from a cerebral edema due to an allergic reaction to the chemical meprobamate (sp?) found in the prescription painkiller equagesic.
Supposedly, Betty Ting Pei couldn't rouse Bruce from sleep and panicked. I think instead of calling for medical help, she called Raymond Chow. By the time Bruce got to a hospital, it was too late.
There have been many goofy stories floating around about his death: Triad assassination, death touch assassination, overdose of hashish, and there are other wingnuts who still think he's alive and the whole thing was faked.
I'll go with the official report. Doesn't really matter anyway. Dead is dead. The hows or whys this long after his death are really unimportant.
Expect only what happens in the fight. That way, you'll never be surprised.