"There's gunfire on board . . . We're going down."
The distress call came from Pacific Southwest Airlines Flight 1771 halfway on its run from Los Angeles to San Francisco, flying at 22,000 ft. Two minutes later, the British Aerospace commuter jet shrieked toward earth in a nearly vertical dive and disintegrated as it slammed into a hill near Paso Robles in San Luis Obispo County. All 43 aboard were killed, including four executives of Chevron Corp. From that baffling beginning, other messages gradually unraveled the mystery of what had happened.
"Jackie, this is David. I'm on my way to San...