[RationalDino]

Or alternately, they staged what appeared to be a fatal accident to put him in a witness protection program.

Or alternately, he did it and then tried to back out of the deal. Now arranging an apparently accidental death then became the best way to keep security intact.

The one theory that makes no sense is that they intended his death from the beginning.

[op00to]

All believable scenarios. I personally am fond of the "pin it on a dead guy" story. I want to believe that western security services have some sense of elegance.