I agree, witness accounts can be of limited value.
Some that is known, were they actually on a LL training route? Was it a formation flight of some sort? If neither of those, what exact type of flight?
What if any local ATC was controlling? Hopefully we don't have to investigate into if either of the pilots were from the area or had interests on the ground.
With no ejection attempt, was it a planned flight close to terrain? If so, how was the weather? There seemed to be some oxygen issues in the recent past. Is that related to this mishap? If that was the case, I would think one pilot would possibly hold on longer than the other, then able to take action.