Growling in Gunnison County, Colorado

My uncle and I were elk hunting near Fossil Ridge northeast of Gunnison, CO when this incident ocurred. It was late afternoon when we noticed a strong odor that we thought might be elk so we headed east toward a small ridge hoping to find one on the other side. As we got closer we heard the noise of rocks being banged together. As we topped the ridge we saw a large dark brown animal squatting at the edge of a dry creek bed with it's back toward us. It was banging 2 rocks together with it's "hands" and making a grunting/growling noise each time the rocks hit. It seemed to sense our presence almost immediately and turned around and looked at us. Then it quickly stood up and jumped across the creek in one motion. I remember thinking "nothing can move like that!". It ran up the slope on the north side of the creek bed at an angle and disappeared into the pine and aspen trees farther up the hill. We could see it for about 50 feet before it was gone from sight. It moved real quietly for something that big. I estimate it's height as 6'5''. It was covered with long dark brown hair that made me think of a yak. It had a strong smell, at least there was a strong smell in the area that was like elk urine. After we calmed down a bit, we went into the creek bed and found the 2 rocks which were chipped and broken. We looked for other signs in that place but couldn't find anything else.