from the clip it looks like he was carrying out a rearward auto! Weird.
Perhaps a more likely explaination is as follows...
You see the image moving R to L start to slow then the horizon tips and the direction of travel appears to reverse L to R.
This is an accurate record of the relationship of heli to the part of the landscape the camera was pointing at.
What is happening is that the camera has stayed pointing at same place (the dam) whilst the heli made a 180 degree ish fairly tight turn (hence the system losing lock on the horizon)
At the end of the turn the heli is travelling in the opposite direction and the camera is still looking at the dam but now the heli and camera are travelling in the opposite direction.
So the shot started with camera looking "nose left" but and finished looking "tail right" or put another way the heli orbited around the camera and reversed direction.
Glad they got out unharmed.
Mickjoebill.