If the pilot was had a stoke or heart attack that will not be to hard to find. Atsb have one thing on there side on this accident and that is the aircraft didn't catch on fire and one would think that they will be able to recover if not most but all of the aircraft.
If it has had a bird strike there will be evidence of that which should be easy to find as we'll. but the main thing is no fire and there fore no lost evidence