I was hiking with my family (myself, my two older brothers, my father, my uncle, and two cousins) as a child, and we camped for the night at PJ Lake. Later that evening, after most of us had gone to bed, my dad and my uncle were still up, and suddenly there was a terrible noise from the woods that sounded like someone screaming, but it wasn't a mountain lion or an elk, as my dad and uncle were both very familiar with the woods in those parts and knew the various sounds of the wildlife in the area. They were also, honestly and truly, scared, and it's one of the only times I'd ever seen them that way, before or since. These big angry howls were accompanied by actual stones being thrown near the perimeter of the camp, basically just outside the firelight. We hadn't seen any sign of anyone camping nearby us, for all we knew, we were alone in the woods that night except the local wildlife. We got no sleep that night, and left early the next morning. In the years since the incident, I've heard similar noises I heard that night and what has been described identically by all who were there, primarily on nature documentaries about primates and the great apes.