A recently discharged USAir employee boarded PSA Flight 1771 after having left a goodbye message with friends. He bypassed security and carried a borrowed 44 caliber pistol. A note written by this passenger, found in the wreckage, threatened his former supervisor at USAir, who was aboard the flight. At 1613, the pilot reported to Oakland ARTCC that he had an emergency and that gunshots had been fired in the airplane. Within 25 seconds, Oakland Center controllers observed that PSA 1771 had begun a rapid descent from which it did not recover. Witnesses on the ground said the airplane was intact and there was no evidence of fire before the airplane struck the ground in a steep nose-down attitude. The CVR tape revealed the sounds of a scuffle and several shots which were apparently fired in or near the cockpit. The pistol was found in the wreckage with 6 expended rounds. FAA rules permitted airline employees to bypass security checkpoints.