I wasn’t there but looks as if the skier above may have put enough pressure and or slice cutting the snowpack to release the slab resulting in taking out the poorly positioned boarder. Sometimes it’s the other guy you need to look out for. The victim was extremely lucky to get funneled out like he did and not become racked up in lunch rocks. Personally I never linger in that area. I have seen many a slide and slough in that zone. Never understand why so many people congregate there. Just a reminder what “Considerable” means:Considerable is the third of five levels on the avalanche danger scale. Under Considerable danger, natural avalanches are possible and human-triggered slides are likely. Avalanche conditions are considered dangerous and careful snowpack evaluation, cautious route-finding, and conservative decision making are essential.
Based on the size of that slab I'd say conditions were quite dangerous and those people probably shouldn't have been there and hadn't checked the conditions online and/or didn't know how to properly assess conditions.