Scuttle has it that Petty Officer Gill was wearing the proper PPE (personal protective equipment) but was likely not hooked into the gun belt when the Seattle accident occurred. He was in the well of the bow of the boat (not "riding on the bow" as earlier reported; the well is an appropriate crew location), and was thrown when the coxswain made a J-turn. Not sure if the turn was at power. The boat might have dug-in during the turn, putting more force on the crew.
This is all pure scuttle and speculation, of course.
As to more speculation & prognostication, I see the full report from the recent CG Academy study being released on Friday.