I'm not sure if it was kids being kids or walkers trying to deter riders or mtb'ers in for a challenge.
But can the asshats who are putting large loose rocks right in the middle of downhill lines at Lake Parra please ... dont!

We spend a lot of time maintaining these trails for everyone's enjoyment and we have a good dialogue with the rangers.
I saw kids on a family ride who had these rocks flung back at each other and a boy fall off.
Not to mention my own otb at a section I've done a hundred times.