[rudderboost]

I'm gonna guess FADEC (Engine/fuel computer) or Auto-Throttle inputs. I think something (or someone) "told" the engines to shut off. By "told" I mean either by failure of a computer (which with redundancy is hard to believe with both engines at once) or an input commanded a spooldown. One thing for sure is pilots around the world are very interested in what happened, probably as much as Boeing is.