As I said before, I more inclined to believe some sort of problem leading to a possible stretching of the glide and stall with subsequent nose down descent into the ground.
Bose
The witness who seemed quite a serious calm sort of guy reported a sharp wing dop followed by an almost vertical dive into the ground. Another witness reported the engine sounding like a high speed drill which for a non pilot was quite an accurate description of the sound of a high rev diving aircraft.
There were no radio calls made in ref to a rough engine or engine failure and subsequent attempted off field landing. Tricky one!
Pace