I remember first time I saw it was on tv, I think I was 10 or 11, early 90s. I missed the first 5 minutes, and had no idea what it was about. I figured it was a Commando kind of movie with Arnie. So the "twist" when the predator shows up after the assault on the camp was pretty damn awesome 
There must have been a door there in the wall, when I came in.
Truly gone fishing.