For many people, the 984 foot fall alone would be enough to trigger a heart attack. Since he was ‘experienced’, he likely had taken deep spills before. He must have had some device still allowing for communication as he was found, even with his spine and other parts of the body wrecked.
Spelunking: Cave exploration for fun and fitness.
Caving: Cave exploration for collection of scientific data.
984 feet? After about 100 feet he’d reach terminal velocity and he’d be doing about 75 mph. Hitting a rock wall at that speed is going to hurt.