Footsteps in Snohomish County, Washington

On Memorial day weekend, we camped every year at the Buck Creek Campground. This year, while sleeping in the top bunk of a small Prowler trailer, I heard several loud thumps on the ground outside the window near my head. I wasn't asleep at the time and became frightened. It sounded like heavy footsteps either walking or maybe running by our camp site. This was at about 11:30PM. The next morning I went out on the steps of the trailer to put on my shoes. At the bottom of the steps we had a rubber mat. This mat was partially sunk into the dirt on the edge of it by a 15"-16" human looking footprint, it was maybe 6" wide and 1/2" deep. It had perfect toes and there was just a slight arch to it. It looked very flat footed. There were maybe 20 of these tracks going by our camp site. I showed my family members and other people in the camp area came by to take a look. I wanted to cast it but nobody was really interested. I was just a kid at the time. I don't think anybody took any pictures either. There were left and right tracks and the step was twice my own. I think it rained just before we got to camp so it might of made the ground easier to make tracks in. I noticed that anything that was on the ground and was stepped on was pushed in as deep as the track bottom. I didn't smell or hear anything else that weekend. I at first thought that maybe someone had made them, as a joke, but after looking at how many of them there were and how deep and detailed they were I couldn't figure out how anyone could of.