So sad. My daughter is working in a ski resort and they recently went, 30 of them to a difficult area in memoriam for a friend who had died in the same off piste area a month before. That's more understandable, pushing yourself to the limit off piste, courting danger because that's your personality. Just having a minor fall which you might as easily have had on the stairs at home and suffering brain injury feels so much more unexpected.
I have always told the children not to hit each other on the head which they have all done occasionally over the years as the head is such a dangerous bit to hit.