What could cause something like that ?
There are obvious answers: coincidence,parts failure,bad fuel ,pilot error,etc.,...and one not-so-obvious possibility: sabotage.
Question: How does one sabotage a helicopter without getting aboard it ?
Answer: With a laser or EMP device - capable of "frying" the on-board electronics.
How far-fetched is the idea ? I found one Net contributor who takes it very seriously:
Looking further, I found someone who allegedly has plans and kits for such devices !!
(Just scroll past the entries for "reversing the meter",and the "100mpg Carburetor".)
Question : Sounds complicated. Why not just hijack a chopper ?
Answer : Suppose you had something bigger in mind- such as an airliner-and were just practicing ?
What do you think ? Tinfoil Hat Time - or something to worry about ??