Don't want to sound gory but the video looks like he tried to save it with his elbow but a couple of seconds after got his throttle hand trapped.
Either that or the bike still turning in stopped him from getting away
The force of the hit from Edwards/Rossi would have pulled the helmet strap through the D rings
either way a very freakish and rare accident
poor bugger, heart goes out, the footage of his girlfriend freaking out in the pits was uncalled for, made the race coverage look like a Murdoch newspaper