It seems pretty clear that this accident is a simul-rap gone wrong. It is easier and safer to simul-rap with a gri gri as you have more control and it is pretty hard to rappel off the end of the rope. Not impossible, but harder than with a standard ATC. There was, a few days before this, a similar rappel accident at Wasootch where the woman did not thread her ATC right and took a 20 metre fall.
Not to be a dick about this - and I certainly didn't climb 5.12 out of the womb and can't climb 5.12 now, but we just came back from climbing Beautiful Century (an OK route, but not stellar) and we simul-rapped the route. With two experienced climbers using a gri-gri, it felt safe, and, was, as I've said before much faster.
Dcipher, calling someone by their (quasi) real name is not, IMHO, an insult. Making up - what 5 aliases? - is an insult to the intelligence of everyone on this board. I don't know why Kevin does not post under his real name, but calling him on it does not constitute an insult.
And, climbing is a lot like driving, at some point, you have to have confidence that you can do some things properly and safely - tie in, rig a rappel, self-arrest, kick some steps - put your seat belt on, change gears, etc. If you have no confidence in your own competence at all, you'll never get off the belay/ground.