I had a similar experience camping with my family as a kid outside of Wichita Falls, I must've been 9 or 10 tops. I woke up one morning in the camper of my dad's pickup instead of in my tent. Groggily trying to figure out what was going on I started to crawl out over the tailgate only to have my dad's hand come around the corner, grab me by the face, and shove me back in, which was sufficient to wake me up enough to realize that there were 15-20 full-sized bison ambling through the camp. One of them even came within a couple feet of the truck. Needless to say I practically crapped my pants because I had never been anywhere near any kind of animal that big before.