I remembered the search for the four 500 pound bombs he had on the racks when he flew into the mountain, .....and Wiki to the rescue.
Craig D. Button - Wikipedia, the free encyclopedia
The Air Force looked extensively into his personal relationships, including one described as unrequited love.
Air Force examines personal relationships of pilot who killed himself
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IIRC, before TSA allowed pilots to carry guns into the cockpit, the pilots requesting to do so were subject to additional psychological screening, as well as training.