The balls are not dangerous, it's the idiots who thought doing it there without bothering to check for the possibility it might just roll off the side of the mountain before trying this stunt.
Idiots will be idiots, hate to be harsh about a death but it's true.
It must feel horrible to be the guy that pushed it away from the people, just to watch it roll slowly down the hill, then bounce over the track and down the valley. Especially seeing him chase it and very nearly stop it.
must hurt
no pun intended