Gun find helps probers

Investigators were considering Thursday the possibility that someone with a gun entered the cockpit and caused the crash Monday of Pacific Southwest Airlines Flight 1771. All 43 people on board were killed. Searchers at the scene of the crash Wednesday found a handgun, and sources in Washington said investigators believe the pilot and co-pilot may have been shot by a former airline employee who had been discharged.

A cockpit recording reportedly showed ``a terrible commotion'' shortly before the crash. One source said gunfire could be heard on the tape of the flight voice recorder recovered from the wreckage of the jetliner. Investigators have not ruled out the possibility that the crew was prevented from flying the four-engine jet because of a struggle or by sudden decompression of the cockpit from bullets shattering sections of the windshield, the sources said.

David A. Burke, the fired airline employee under investigation in the crash, owned a ``legal handgun,'' said Assistant United States Attorney Steve Czuleger in Los Angeles. Mr. Burke, fired last month by USAir, which owns PSA, is believed to have carried a .44-caliber Magnum handgun aboard the plane seeking revenge against former boss Ray Thomson. Both were among the victims.