Depending on weather, once you are 10+ feet from the tent in the dark, you could be in big trouble. The trail of bodies flows from there. Some walk, some stay put, others move later, some fall/slip and are injured... nothing here seems very odd.
Now, what happened to freak them out? It could be any number of things. The sound of a suspected avalanche coupled with a tent pole failing could start a panic. An aircraft could sound like an avalanche. An aircraft dropping a few flares could also put them in fear of incoming weapons. Or it could just have been someone shouting something at exactly the correct time. The power of suggestion is hard to fight in such a group. The group feeds on itself. Someone says "run" and the herd moves.