>>The only time it happened, both pilots were shot by a mad pax. California, 1986 or 87 if I remember correctly.<<
Actually, it's happened at least a couple of times in California:
______________________________________
05/07/1964 Pacific Air Lines
Fairchild F-27A San Ramon, California
The aircraft went into a steep dive and crashed while on a flight from Stockton to San Francisco, CA . The last message which had to be obtained through laboratory analysis was "Skipper's shot. We've been shot. I was trying to help." Francisco Gonzales, a passenger, who had told several people he was going to kill himself, shot both the pilot and co-pilot.
12/07/1987 Pacific Southwest Airlines
BAe-146-200a San Luis Obispo, Calif.
A fired USAir employee, David Burke, after leaving a goodbye message to friends, shot both pilots. The aircraft went into a steep dive and crashed.
http://planecrashinfo.com/unusual.htm