I had someone I know die recently.  Circumstances were very unusual.    He began to breathe so hard, all body and hands began to shake, and his lips were green.   He took some medicine and it subsided, but a few minutes later, it started again.  The ambulance was called, but the person died.  Judging from that, what would you say it was that could cause death so sudden?
Hi, I am sorry for the lost of your friend. There are various causes to his death; further details on his medical history are needed for a more specific opinion