Hi I'm Curious Of What Caused The Death Of My

Hi I'm curious of what caused the death of my friend.about a mouth ago he was getting shortness of breath,went to the hospital and they found nothing. Went back again about a week later with the same thing, nothing found.3 weeks later he woke up in the morning not feeling well... Sweating... Then had some sips of water then fell from the bed and started foaming from his mouth. Then died.what are the possible causes of his death?