There were actually 4 deaths on the same day. One climber on Mt St Piran in the Rockies, one boarder inbounds at Big White, and two snowmobilers in separate events in the Kootenays.
In the case of the Big White death, the slope had been avalanche controlled, skiied thousands of times the previous day, and in fact skiied by patrollers several hours before the avalanche occurred on the day of the incident. All indications point to rising temperatures setting off an unexpected weaknss deep in the snowpack. Given that pretty much everything possible was done to reduce risk and in fact, the slide caught even trained professionals by surprise, it goes a fair way to illustrating the concept of irreducible risk. If you are unwilling to accept this level of risk, staying home is a good option.