Unfortuntaely, as an ATCO, I've experienced this sort of incident before, i.e aircraft stops communicating.
Whatever was the cause, it happened very quickly and I'd be very suprised if ice was the major factor but the investigating authorities will make their fndings known ASAP.
All credit to the people in charge on the ground and their responses to the media, it's clear that their prority is to anyone on board and their relatives.
Whoever is coordinating all of the terrible events - well done to you.