What happened in this accident to cause the N3 to "flip over" in the early stage of launch?

On Tuesday, December 6, 2016 at 7:15:05 AM UTC-8, Jock Proudfoot wrote:
At 14:06 06 December 2016, Jock Proudfoot wrote:

Footage of the accident, in which the victim was dragged upside
down along the runway, was recorded on the centre's CCTV and is
now being studied by accident investigators.

http://www.heraldscotland.com/news/1...pilot_killed_i
n_freak_accident_during_take_off/