Maybe the man was a parachutist who had jumped out of the plane and it had failed to open, landed ON the beach as opposed to swimming and the last thing he saw before he died of his injuries, was the plane???
1.It could have been a remote control plane (out of control) and heading straight towards him.
2. Something may have been ejected from the plane.
3. The plane may have dropped a nuclear bomb.
Any good ?