Screaming or howling in Daggett County, Utah

In 1989 I heard something out in the mountains that I had never heard before and have not heard since in the wild. In early October I met a couple of hunting buddies at a predetermined location where we would setup camp for the Rifle Elk Hunt. My friends had arrived several days prior to the start of the hunt and scouted the area on horse back. I arrived 2 days before the hunt was to start to also scout the area. The area that we were going to hunt was on the North Slope of the Uinta Mountains. We chose a secluded high mountain meadow (park) with thick dark pines on one side and mixed aspens and pines on the other. We had setup camp at the top of the park next to a rising hillside of aspens with a stream close by to water the horses. We lashed downed aspen trees to the living trees to make a corral for the horses so that they would not have to be hobbled or tied. The jeep trail to our camp was very long and rough. Downed timber had not been cleared for years. The trucks and horse trailer had to be bounced over numerious dead falls in order to reach our camp. Arriving at camp early in the evening 2 days prior to the start of the hunt I started cooking dinner with my 2 hunting friends. The sun had already set and it was between 8:30 - 9:00 in the evening. We were cooking steaks on a camp stove. There was some noise from the hiss of the stove and lantern, snapping of the camp fire and sizzle of the cooking food. The camp fire was situated between the table where we were cooking and the tree line where the horses were standing and watching us prepare the meal. The area aroung the horses, trucks and tent was lightly illuminated from the light of the fire and lantern. One of my friends had gone to his truck or the tent to retrieve something while my other friend and I continued cooking. We were talking about areas the we were going to scout the following day when we heard a very loud and deep resonating roar which lasted for 3 - 4 seconds. We both stopped talking and looked at the horses to see their reaction (it didn't phase them). I had a reaction - the hair stood up on the back of my neck and on my arms. I ask my friend if he had heard that and he responded that he had and asked what it was. I answered that I didn't know. With out another word between us we both went to our respective vehicles and loaded our rifles. The other friend did not hear the roar. The sound eminated on our side of the crest of the hill west northwest of our camp position at a distance of approximately 300 yards. I do not know what it was however I do know what it was not. None of the known animals native in that area make a deep resonating roar like I heard. Furthermore only a very large animal could have made such a deep sustained resonating sound that could carry for that distance. Bull Elk are very vocal at night however the rut had passed and no whistle, chuckel or grunting was present. Elk will screem when mad but it is a higher pitch than what we heard and shorter. Moose and Deer just don't make loud voulmetric calls. Bears, cyotes, foxes, and cougers are higher pitch and do not resonate. A really big bear might be able to make such a deep sound for that duration however no bawling or drop of tone was present in the roar. I have investigated numerious sounds to see what comes close to what I heard. A year ago I found a recording of a roar from a large Gorilla on the internet and this is the sound I heard in the mountains that night. Unfornatuly I didn't save that web site. The sounds recoded on the BFRO Web site described as howls or screams are very similar, however what I heard was missing the higher pitches or howling noises. Perhaps they were present but drowned out by the camp stove and lantern. I thought that it was odd that the horses didn't get spooked at the roar but I didn't note the direction of the wind when this happened. Usually scent has to accompany a sight or sound for the horses to spook.