The Essendon Terminal Information (ATIS) advised of surface wind from 260 degrees at 15/25 knots. The pilot had completed the flight and was making his landing approach at 75 knots with 40 degrees of flap set. From Essendon Tower the aircraft was observed to descend rapidly from a height of about 20-30 feet and contact the runway heavily, nose wheel first. A bounce followed and then the aircraft touched down again. Aware that the nose wheel was wobbling violently and that the nose attitude was unusually low the pilot steered the aircraft off the runway, shut down the engine and evacuated.