First, my mini-rant: That's not a "shelter" it's a freaking corral. Thank you. It feels good to get that out of my system.
The rock with sharp sticks would probably leave quite a mark, but it does not appear to have enough momentum to be fatal.
There was not enough of a picture to convince me that those "pungi stakes" would really do a number on someone who fell flat on them. Not because they are not sharpened on the end, but because they a) look to be rather shallowly planted, thus more likely to pop out than stay and drive through, and b) they look as if they will bend if they do not actually pop out of the ground.
Conclusion? Freaking rank amateurs not only commit felony stupidity bordering on capital stupidity, but probably screwed up in constructing a shelter, setting traps that will be lethal, and somehow conecting themselves via social media to the whole thing.
It's like they need to be taken out of circulation for their own protection.
stay safe.