Avalanche accident in Davos, Switzerland

We were a group of 4 skiers taking a freeride route in Davos Parsenn (from Weissfluhjoch), this route is prepared and inspected by the resort for off-piste riders. When going through one of the steeper faces, a slab avalanche broke and took one of the skiers down. See full video and analysis of what happened and what we did. Feel free to comment on what was we did wrong or right.