No "inside knowledge" but a bit of time in 212/412, plus experience of overpressured float bottles
I've just spoken to someone who was there at the time, and the float bottle was being removed when the valve let go for reasons yet to be resolved. Most of the force was into the airframe, but the young engineer received groin injuries and was knocked to the concrete floor and hit his head which then split his ear as well. He is expected to make a "full recovery", but from injuries that you and I would probably rather avoid in the first place
It was a Helicorp machine, not Australian Helicopters.
I stress that this is second hand gen: the ATSB report will be the definitive source of information.