USAir, which had recently purchased Pacific Southwest Airlines (PSA), terminated David A. Burke, an aircraft cleaning specialist, for petty theft of $69 from in-flight cocktail receipts; he had also been suspected of involvement with a narcotics ring. After meeting with Ray Thomson, his manager, in an unsuccessful attempt to be reinstated, Burke purchased a ticket on PSA Flight 1771, a daily flight from Los Angeles International Airport (LAX) to San Francisco International Airport (SFO). Thomson was a passenger on the flight, which he regularly took for his daily commute from his workplace at LAX to his home in the San Francisco Bay Area. Flight 1771 departed from LAX at 15:31 PST, scheduled to arrive in San Francisco at 16:43.
Using USAir employee credentials that he had not yet surrendered, Burke, armed with a Smith & Wesson Model 29 .44 Magnum revolver that he had borrowed from a coworker, was able to bypass the normal passenger security checkpoint at LAX. After boarding the plane, Burke wrote a message on an airsickness bag, but it is not known if he gave the message to Thomson to read before shooting him. The note read:
Hi Ray. I think it's sort of ironical [sic] that we end up like this. I asked for some leniency for my family. Remember? Well, I got none and you'll get none.
As the aircraft, a four-engine British Aerospace BAe 146-200, cruised at 22,000 ft (6,700 m) over the central California coast, the cockpit voice recorder (CVR) recorded the sound of someone entering and then leaving the lavatory. A Mayday episode suggests that this was Burke entering the lavatory to draw his revolver discreetly, possibly loading it and giving Thomson time to read the note before killing him. Captain Gregg Lindamood, 44, and 48-year-old first officer James Nunn were asking air traffic control about turbulence when the CVR picked up the sound of two shots being fired in the cabin.
The most plausible theory as to what happened was deduced from the pattern and audible volume of the shots on the CVR. According to the Mayday episode, it is likely that Burke first shot Thomson twice. Thomson's own seat was never recovered. Part of a seat that was identified from its serial number as being directly behind Thomson's was found to contain two bullet holes. As a result of the revolver's considerable power, the bullets could have traveled through Thomson's body, his seat, and then through the seat behind. First Officer Nunn immediately reported to air traffic control that a gun had been fired, but no further transmissions were received from the crew. The CVR then recorded the cockpit door opening and flight attendant Deborah Neil telling the cockpit crew, "We have a problem!", to which Captain Lindamood replied, "What's the problem?" A shot was heard as Burke shot the flight attendant dead and announced "I'm the problem." He then fired two more rounds. Most likely, he shot the captain and first officer once each, incapacitating them, if not outright killing them. Several seconds later, the CVR picked up increasing windscreen noise as the airplane pitched down and accelerated. The remains of the flight data recorder (FDR) indicated Burke had pushed the control column forward into a dive.
A final gunshot was heard followed not long after by a sudden silence. It is most likely that Burke killed Douglas Arthur, PSA's chief pilot in Los Angeles, who was also on board as a passenger and who may have been trying to reach the cockpit to save the aircraft. There was speculation that Burke shot himself, though this seems unlikely, because a fragment of Burke's fingertip was lodged in the trigger when the investigators found the revolver. This indicated that he was alive and he was holding the gun until the moment of impact. The plane crashed into the hillside of a cattle ranch at 4:16 p.m. in the Santa Lucia Mountains near Paso Robles and Cayucos, exploding on impact. The plane was estimated to have crashed slightly faster than the speed of sound, at around 770 mph (1,240 km/h), disintegrating instantly. Based on the deformation of the hardened steel black box data recorder case, the aircraft experienced a deceleration of 5,000 times the force of gravity (G-force) when it hit the ground. It was traveling at an approximately 70-degree angle toward the south. The plane struck a rocky hillside, leaving a crater less than two feet (0.6 m) deep and four feet (1.2 m) across. The remains of 27 of the passengers were never identified.
After the crash site was located by a CBS News helicopter piloted by Bob Tur, investigators from the National Transportation Safety Board (NTSB) were joined by the Federal Bureau of Investigation (FBI). After two days of digging through what was left of the plane, they found the parts of a handgun containing six spent cartridge cases and the note on the airsickness bag written by Burke, indicating that he may have been responsible for the crash. FBI investigators were able to lift a print from a fragment of finger stuck in the revolver's trigger guard, which positively identified Burke as holding the weapon when the aircraft crashed. In addition to the evidence uncovered at the crash site, other factors surfaced. Burke's coworker admitted to having lent him the gun, and Burke had also left a farewell message on his girlfriend's answering machine.