who could it be?

Last night we went "creature hunting." I was taken to some middle of no where place, where we walked through a forest until we reached a river bank and built a fire. We had 3 guys and the guys I was with had every intention of killing this creature. Let me tell you about him. Supposedly here in rexburg a number of people have seen this "creature" Its about 5 feet tall and stands on it's hinds legs. It has amazing strength, as in it can chuck 10 pound rocks 40 feet into water. This is kind of it's "scaring" tactic, for every story I was told had him throwing these huge rocks into the water every 15-20 seconds. And of course we were on the river bed where many people have seen it. So while I'm still a little skeptical about it all, last night I was pretty freaked out and I didn't care to have proof that it was true and thankfully I never got the proof.