My 39 Year Old Brother Was Found Deceased In The

My 39 year old brother was found deceased in the back seat of a veh. One hour earlier had been into a local wal mart and purchased a watch. He picked up someone needed a ride who wrecked an hour later, the vehicle my brother had been driving. Autopsy said .12 alcohol, no drugs in system but was death by natural causes, chronic alcoholism (liver abnormality). Office at scene said he noticed only a white substance from my brother's nostril. Any idea what could have caused that?