A low hum in Palo Pinto County, Texas

I was 14-15 years old. My father and I were camping with another father and son along the Brazos River. It was after midnight and my friend and I were running a trotline we had stretched across the river. As we approached the opposite bank from our campsite, we heard what was to this day an almost indescribable sound on the bank. It was a combination of a low frequency howl with varying low pitch grunts and growls. We immediately froze and shined our flashlights at the bank. There was a steep drop off into the river with a patch of evergreen shrubs and driftwood about the size of a single car garage. This vegetation started a few feet from the water and extending two thirds of the way back up the bank. Our flashlights were poor, as were most from this time period, and we could see nothing. We were within 30 feet of the bank and we both knew exactly where the sound originated. Whatever we heard was behind the described vegetation, so it was obscured. A second vocalization occurred within 10-15 seconds of the first. The first time it ”sounded off” lasted less than 10 seconds. The second time was considerably longer, louder, and the meaning seemed clear. The first sound was a warning, the second time was threatening. There was no howl the latter time, only grunts and growls directed straight toward us. It was loud enough both times to be felt in your chest, similar to a large bass speaker in a car, but stronger. We dropped the trotline and fanatically rowed our canoe back across without saying anything. When we reached the bank we ran back to our camp which was approximately 40 yards from where we landed. Both adults were up and out of their tents asking us, “What was that?’ My father was a Marine and State Trooper. He was rattled by what we heard. The straight line distance from the vocalizations to our camp was 150+/- yards. The sound was loud enough to wake both adults. We planned to spend two nights at that site before continuing down river but left the next morning for a campsite 6 miles downstream. The trip was to last five days but we cut it to two nights due to being very unsettled. My father and I had both spent our lives hunting and fishing. I was comfortable in the woods and an accomplished outdoors man. I was a Boy Scout for years and had camped on that same spot in the past. What we heard was nothing I can explain. I know of no animal that can make those sounds, particularly in the combination we heard and the low frequency pitch we experienced. Whatever made the sound was massive and seemed mammalian. The experience haunts me to this day. I’m not afraid in the woods, but the experience still follows me. I wish I had seen it just to verify what I believe it was. The interesting thing is, that even at the time, I knew what it was. There was, for me, no other explanation. I feel privileged to have what I know must have been a Bigfoot encounter, even if it left an indelible mark. Width of the river was roughly 50-70 yards. Embankment where vocalizations occurred from top to waterline was 15-20 ft. It was a relatively sandy bank that was nearly vertical.