A group of snowmobilers were on or near slopes on the south/southeast side of Mount Brewer in the Purcell Mountains. Two were caught in a very large Deep Persistent Slab avalanche 200-400m wide that ran 900-1100m onto a small lake. One deceased with an activated airbag was recovered from a two metre deep burial. A transceiver signal was located on the lake where debris was floating on the water. The second deceased was subsequently recovered from the lake by a dive team.