Screaming or howling in Cowlitz County, Washington

The year was 1970 and my friend John and I rode my Honda 90 along logging roads to a secluded area which was about 7 miles from my family's cabin on the Toutle River. The USGS map of about 1952 labeled the road as Rock Creek Road and it intersected the Tower Road just about 150 yards NE of Hollywood Gorge. I remember the year because John had been graduated from high school and was working at Longview Logging and Mill Supply and I was about to enter my junior year of high school. Anyway, it was summer and we were camping in my father's old army pup tent when we heard what sounded like several apes screaming. We both agreed that was the best description of the sound. It was fairly dark and we looked out of the tent and saw a large dark silhouette about 150 feet from the front of the tent. John had a JC Higgins single shot 22 rifle and I had a Winchester gallery gun also in 22 cal. What we saw we thought was a big foot and we shouted out several warnings to whoever or whatever was there that we were going to begin shooting. After getting no response, we pumped several rounds into it and it did not move. We finally got brave enough to go out and investigate only to learn it was an old tree stump from when the area was logged by McCormick Brothers in the late 1800s or early 1900s. Although the stump was not a big foot, we both heard that most chilling screaming which must have lasted 45 seconds to a minute. My best guess is that the sound originated less than 300 yards away, yet the nearest farm or house or cabin was about 1-2 miles away.