I just read on Fox that the airplane was intercepted at 34,000 feet. The pilot of the F-16 stated that oxygen masks inside the cabin were deployed and that the pilot of the airliner was slumped over. The F-16 pilot further stated that he saw 2 people moving about inside. At 34,000 feet there isn't sufficient oxygen to sustain life for a long period of time.
Moving about the cabin would undoubtedly have been with the aid of the 'extra' mask at the aisle. Some knowledgable passenger may have tried to help but probably couldn't get into the cockpit in time.
Bodies from the crash site were FROZEN. All of them.