You hear a bang as it touches down then it goes wobbly with a sudden decrease in RRPM. As if he put a wheel on a rock and it slipped off. But that wouldn't explain the decrease in RRPM which gets pretty low during the wobbles before the rotor blades whacked something. Unless he had an engine failure on touchdown and tried to take off again, but at 13,000 feet altitude that was never going to work.