Screaming or howling in Idaho County, Idaho

This incident happened in Sept of '74. I was 15 years old at the time. I was part of a party of 10 that had packed 20 head of horses into the Idaho wilderness to hunt for elk. We set up camp approx. 26 miles up the Boulder Creek drainage off the Lochsa River. During the pack-in, we incountered 2 hunters from the Boise area that had a once-in-a-lifetime bighorn sheep tag. They camped in the next valley over from us. It was the 2nd day of the hunt and I was paired up with an oldtimer named Louie who had spent much of his life in the mountains of Idaho. We had made it about 5 miles from camp in the morning and were almost to the top of Stanley Butte when we noticed that there was absolutely no sounds anywhere.....none...no birds, no squirrels, nothing. We commented about it, but really didn't read too much into it. As we got to the top of the Butte, the horses started to get extremely nervous. This concerned us since both horses were not afraid of bears or cougars (we had ridden past and packed both types of animals on these horses several times)It got to the point where we were having a hard time holding the horses. We rode about another 50 yards and came across some huge footprints...they were not bear tracks....very human in form and very fresh. Louie turned absolutely white (the first time and only time I ever saw him scared). He immediately stated that we should get out of there...now!! When we got about a mile away, the horses settled down. Louie told me that no one would believe us, but he had never seen any thing like that in all the years he had spent in the mountains. Neither of us said much about it after that. The following day I was hunting with a different fellow and we headed (by my choice) in the opposite direction. As we were riding down the trail, we came across the 2 hunters with the sheep tag. They were packed up (sloppily) and headed out...without their sheep. We asked why and one of the guys said we would never believe him. After some prodding, they told us that their camp had been destroyed by a "log-throwing,screaming animal". They had not slept since the prior night and were visibly shaken. The tracks Louie and I had seen were headed in the direction of their camp. A few weeks ago, a young man who is the son of one of the men I was hunting with on that trip, told me that Louie had told him the story before he (Louie) died. The area we were hunting is very rugged. The tracks we saw came out of Old Man Canyon. It is so thick in there that anything could go undetected. I've always wanted to go back into the bottom of that canyon and search for evidence, but have never quite gotten the time...or the nerve.