Finally got some vacation time and took my son "primitive" tent camping for four days in Allegheny National Forest. We found a decent site off the beaten path near where we've hunted in the past.Bad weather did'nt ruin our trip much, glad for the time. But yesterday we left camp for a couple hours to make a food run. On our return we turned onto the short rd to our camp, noticed a small pick up truck parked at a trail that led behind our site. Figured it was someone archery hunting. Wrong! I was relieved to be off of work and relaxed out in the woods. We entered our camp, walked around talking. Stopped and was talking with my 15 yr old when a fist sized rock flew past my head between us! I did a what the hell, obvious only a human could launch that. Looked hard in direction it came from. Leaves had turned and I could'nt see any sign of anyone. I told my son to stay in camp, gave him my back up pistol. Walked a 360 degree circle around that point. Tracks in mud (it had been raining constantly, so they were fresh)went down trail towards that truck. I went back to my son told him hold tight I walked fast back out road I had come in on to see if I could get a look at who this was. As I got to the road, two WM mid 30's exited that trail, got in their truck and hauled ass my way. They had'nt seen me I guess. Was wearing a desert gortex parka and kaki pants that blended in well . They slowed as they saw me and passenger glared at me like he was mad as hell. I was so busy giving it back to him and getting physical description. I only got fair description of truck, no plate #. They hesitated as if they debated stopping. But left. I thought maybe because I hadnt been wearing my parka at camp and probably saw sidearm then. I concluded since they were not in hunting clothes and where they parked. They were probably in camp to see what they could rip off. Otherwise anyone else would simply have driven down there. I did not notify police, but did stop and let some other campers know to keep an eye out. They had seen the vehicle and noted they acted suspiciously. Four former Marines who were likewise armed. Did'nt want a run around from police so we just stayed alert last night in case they returned. Let my guard down, bothers me I let two men approach undetected like that. Had to be less than 25 meters best guess from us when one of the two threw that rock.Nothing stolen, but I had loaded anything of value in car so as not to leave anything I could'nt stand losing.Good thing..