Secondly, what exactly happened – was the plane hit by air defence weapons? Was there an explosion on board?
I am far from an expert (i.e. not at all knowledgeable on this stuff) but looking at the video the plane seemed to drop like a rock with no control whatsoever. Unless the wings came off I don’t think planes usually crash like that from some internal mechanical failure (not including a bomb or missile in that). Maybe @LSLGuy or another of our pilots will have a better guess.