Voices in Skamania County, Washington

My son and I were elk hunting in November 1997, and were standing on a ridge overlooking a semi-forested flat area below us. The ridge we were on was fir trees and heavy brushy groundcover, and the area between us and the flat at the bottom of the ridge could not directly be observed. As we were watching the flat below us for signs of elk, I heard what I thought was two hunters slowly walking up the ridge and softly talking to each other. I could not make out any words, only the soft murmuring sound of a voice. I told my son, who was to my left and about ten feet from me, that I hear two hunters coming toward us and we'll let them come up so they know we are there. Just as I said that, we heard a heavy thumping sound, which later I thought sounded like heavy footfalls, going back down the ridge, and suddenly saw a flash of black at the bottom of the ridge as something vanished into the trees on the flat. At this same time, my son snapped his .300 Winchester magnum rifle to his shoulder and looked through his scope. He had also seen the black object as it emerged on the flat. I asked him what the hell was it, and he said, "dad, I don't know what it was ." He said whatever it was, it was big, black and moving fast into the trees. We both decided it was a black bear, but later on back at camp, we talked about it and there are a few questions that we can't answer. 1. Bears are't very vocal, and I was thoroughly convinced I heard human voices coming toward us. What did I hear? 2. We heard distinct heavy footfalls running back down the ridge. A bear runs on all fours, and we did not hear the sound of brush being ran through. What was running down the hill away from us? 3. What was the black, fast-moving creature we both seen briefly at the bottom? 4. Would a hoaxer take a chance like this during elk-hunting season and hunters with high-power rifles? I have lived and hunted in this area my entire life and think about this encounter often. 5. We know it was'nt an elk, deer, cougar or bear, so what was it?