The airplane was substantially damaged at 1830 Eastern time while landing. The Airline Transport pilot received serious injuries, and the second pilot, also a certificated Airline Transport pilot, received minor injuries. Visual conditions prevailed for the local parachuting flight, which also involved an evaluation of the first pilot. Following a passenger drop, the pilots discussed single-engine operations. The first pilot subsequently reduced the right engines power to flight idle, and feathered the propeller. During the final leg of the traffic pattern, the airplane crossed over a fence near the runway threshold, and the first pilot pitched the airplane downward. The nose landing gear then contacted the runway hard, and the airplane began to bounce. After two bounces, the first pilot increased power on the left engine to full power, and pitched the airplane up. He then told the second pilot that he was going to abort the landing, and to reduce the flap setting to 10 degrees. The airplane continued to pitch up, yawed to the right, and stalled at an attitude about 25 feet above ground level.