One man was killed, another was seriously injured and six airplanes were damaged when a gun undergoing maintenance on the carrier USS Nimitz in the Arabian Sea accidentally went off Wednesday, causing a fire on the flight deck, the Pentagon said. Pentagon spokesman Maj. John Smith said the accident occurred Wednesday morning in the north Arabian Sea. "The Nimitz was not conducting flight operations at the time of the incident," Smith said. "The fire apparently started when a gun on an A-7E aircraft fired during routine maintenance, which resulted in a round of ammunition striking an A-6 aircraft and starting the fire," he said. Smith said the injured man was being evacuated from the Nimitz and an investigation into the incident was under way.