Untitled Sighting

We were about a 1/4 mile up the trail from the river. We were walking relatively quiet and slow along the path when we stopped on the path for a moment for my son to tie his shoe. As I waited, I surveyed the thick redwood area above. As I looked, I noticed something moving about 150-200 feet in the distance next to a large old redwood stump. The more I looked, I began to see more mass of the creature. I finally realized what it probably was and what it was doing. It had a human-like torso (from the waist up) and it appeared as if it was scratching its back against the stump. I gained a back and profile view before I could no longer overcome the intense fear I was experiencing. I urged my son as serious as could, to run as fast as he could. After running for about thirty seconds to a minute, we stopped. I wanted badly to go back and investigate, but understood I could not do this with my son. I know the EXACT location of where the stump is and I plan to go back within the week. I hope to find something at the stump.