Report 6868: Campers hear late night screams near Pollack Pines

The weekend of August 16th my family and I went camping on Union Valley lake.  We had three tent sites about a 100 yards from the shore. On Saturday night my 2 year old son had trouble sleeping and kept me up.  I'm guessing it was around 1 or 2 am because of where the moon was.  About 200 yards to the south of our site in the woods this very loud and drawn out scream rang out.  I immediately stopped moving to try and see if I could hear any movement.  Then, from the west across the cove, the same sound responded.  The scream from the west continued at least 15 to 20 times.  There were other campsites and I remember seeing someones shadow as they walked to the bathroom.  The screams got louder and the individual hurried to the bathroom letting the door slam behind him.  The screams stopped and did not return.  My wife and two kids slept through the whole thing which surprised me considering how loud the scream was.  The next morning I asked my father-in-law and my wife's uncle, who were in the other sites, if they heard the screams. Both them and their wives heard them as well.  My father in-law, and my wife's uncle thought it might have been a group of coyotes, but we all agreed that we never heard anything like that before in our lives.  I can usually immitate any sound, but this scream was impossible for me to mimic. It was too loud for me to do.  I have listened to all of the audio that I could find and the recordings in Pallyup Washington are similar.