The feeling of being watched in Guernsey County, Ohio

I was catfishing by the spillway that runs out of Salt Fork Lake at around two o'clock in the A.M. I was only about 15 yards from my vehicle and had been there for about 1 to 2 hrs. I had a Coleman lantern which was lit and about 4 ft. away. The hole I was fishing is approx. 25 yrds across. On the opposite side is a small gravel parking lot. At the edge of the lot is a small line of sapplings. They are growing about 10 or 15 ft. above my line of site. At around two o'clock A.M. I had the strangest feeling that I was being watched. Now let me say this, I'm not an amateur outdoorsman. I was born and raised in the area and at one time hunted anything that walks, crawls or flies. Bowhunting for whitetail deer was my favorite thing to do for years. I've always been in tune with my surroundings when in the woods. At any rate, I had a headlamp on and that was my only source of directional light. Things were very quiet. No bug or frog noises that I can recall. That added to the erie feeling I had. I turned on my headlamp and scanned the line of sapplings across the water from me. I stopped when I lit up a pair of eyes staring straight at me. It was a little freightening at first but I told myself it was a deer. I kept the light trained on the eyes for about 30 secs. or so. They didn't so much as flinch. I then stomped my foot on the ground and snorted like a deer ( a sort of warning sound they emit when spooked). Typically this will cause a deer to give the same warning "snort" and abruptly run off. No such result. The eyes never diverted for a moment, There was still no movement or response of any kind. This is the point in time that I became quite concerned. Almost in a panic, I picked up several rocks and pitched them in the direction of the eyes. Once I'd thrown the third rock or so, the eyes moved away, directly back, like a person walking backward. This is also atypical of deer behavior. They always turn about 180 degrees and trot or run. There was still no noise as the animal did this. It then turned to its right (as best I could tell) and calmly, with no noise, walked toward the brush/ Wills Creek. I then quickly gathered my gear and left. I must say, I was fairly shaken up by the behavior of this animal. Keep in mind, my headlamp was only strong enough to light up its eyes and not whatever they belonged to. I would estimate the animal to be approx. 5.5 to 6 ft. in height. This also clued me in that whatever it was. It was not a deer. In the past I have also heard a sound like something beating a log on the side of a tree. I realize now this is primate behavior. Once again this was late at night while I was catfishing from a boat. It occured shortly after I had turned my nav. lights on and then off again.