Growling in Sublette County, Wyoming

At dusk two boy scouts on a backpacking trip in the Wind River range of Wyoming were exploring the shores of Junction Lake. They heard a growl that they attributed to a bear and began to climb a slope at the north end of the lake. The sound was heard a second time and the boys felt that whatever it was was too far away to bother with and started back down the rocky hillside. As they descended they heard something behind them and turned to see an animal about ten feet away step out from behind a tree. Upon seeing the scouts, the animal vocalized, turned and walked away on two feet swinging its arms. The boys said that the thing was brown with a darker brow area, and that it was on two feet the entire time that they saw it. They reacted much the same way it did to the encounter. They turned and ran back to camp. It was in camp that I heard the story first hand from the two boys only minutes after the encounter took place. I am one of three adult leaders that were on the trip. I tried to convince them that they must have seen a bear or some other animal, but they were insistant that it was exactly what they descibed, and walked on two legs swinging it's arms. I am convinced that they are not making the story up, and did in fact witness some sort of animal on the shores of Junction Lake. They never mentioned the word "bigfoot" -- they just said that they had seen something "freaky". It was one of the other leaders that suggested they had seen a yeti, and I reminded them that it was called sasquatch in this neck of the woods.