The aircraft was on a local flight involving a parachute jumping activity. In addition to the pilot, there were 12 parachutists and an observer on board. The pilot initiated his takeoff on runway 18. A witness stated that shortly after takeoff, the engine power was reduced to climb power, followed by the gear retraction. Reportedly, the aircraft had climbed to about 150 ft agl when the nose pitched up, th plane rolled to the left and then it crashed in a steep left bank, nose down attitude. An investigation revealed that the aircraft was loaded well beyond its maximum gross weight and aft cg limits. The amount of fuel on board was not verified, but even with no fuel, the plane would have been about 580 lbs over the maximum limit. With 100 gallons, the estimated gross weight would have been about 9939 lbs with the cg at about 121 inches. The maximum certificated gross weight was 8750 lbs with an aft cg limit of 117.6 inches. Extensive ground fire damage, but no preimpact, mechanical discrepancies evident.