Or... they all got wet on the way there, and were exposed to high winds, and got hypothermia. One or more of them started experiencing extreme sensations of (perceived) overheating (see paradoxical undressing) and cut open the tent to escape (maybe the door was frozen shut or covered with a snow drift). So far, no mystery. Then others reaching the same state of deluded panic follow suit and run in search of any way to cool down. Some of them run into the ravine seeking water. a deluded thing to do, but again, see paradoxical undressing. Some fall and get injured. Some not at the same delusional stage go out with their clothes on, trying to find their companions. Eventually all of them freeze to death. Subsequently, hungry animals happen upon the scene. What's left to explain?