I have read two versions of the conspiracy theory regarding the crash.
They both involve the aircraft being intercepted by Fuga Magisters (sp?) being flown by mercenary pilots. The first version was that the aircraft was shot down whilst on approach. The second version was that the Magister was unable to locate the DC-6 and the crash was a miscalculation on the part of the pilots.
In the first version it was said that the one surviver of the crash was subsequently shot by persons on the ground and that there was a considerable quantity of ammunition on the aircraft.
Personally I think the pilots erred. Conspiracy theory is usually a load of bunk and is dependent on an enormously complicated chain of events to work. Something not often found in real life.