This reminds me of a situation I experienced when I was about that same age while squirrel hunting. A high school friend and I went squirrel hunting in some MTNF. An old logging road wound along a ridgetop, and we agreed that he would hunt on one side of the trail and I would hunt the other side. We both agreed not to cross the old logging road and to stay on our own side of the woods.
We split up, and I almost immediately found a grove of hickory trees, and the squirrels were thick in this bunch of nut trees. I killed several with my .22 rifle and was having a blast just slipping along and finding shots. At one point, a squirrel came down a tree and was hanging on the side, giving me the stink eye, and I put the crosshairs on him. While I was trying to steady down on his little noggin, I realized there was movement in the scope beyond the squirrel. I lifted my head off the stock and looked, and was surprised to see my buddy had crossed the logging road and was on my side of the woods. He was easing into my hickory grove from across a holler. I yelled at him and stood up, waving my arm at him. He waved back, and I went over to him and asked what the heck he was doing on my side of the road. His excuse was that there weren't many squirrels on his side, and he had heard me shoot several times, so he knew there were squirrels on my side. He had walked over the top and from there saw the limbs swishing across the holler and on the opposite hill. Right where I was.
If I had shot at the squirrel with him in the scope, I don't know if it would have hit him or not. The squirrel was on a small tree, and the tree would have stopped the bullet. However, if I had missed by very much, the tree wouldn't have caught the bullet, and my hunting partner that day was across a small holler on the other hill. And inside my scope's field of view. He was still probably 80-90 yards away and across the holler with woods between us. I certainly might have hit him, being in the scope's field of view. It scared the hell out of me. I brought him over and we hunted together to finish the morning out. He didn't seem to think his crossing over to my side was that big of a deal. I never hunted with him again.