Untitled Sighting

I was driving back from Blythe and it was about 10PM   I slowed my semi down going through the mountains when I came to a pull out, and I got out to relieve myself. While I was standing on the passenger side of my truck, that’s when I heard a sound of rocks falling.  When I looked up, I saw something that I can’t describe in words.  It ran 20 yards in front of my truck heading east; I jumped back in my truck and drove off.  I’ve never told anybody about this not even my wife, because I thought people would think I am crazy.  I have never drove that highway again at night.  What I saw was about 7 or 8 feet tall, it was grayish brown, and what scared me the most was the grunt it made when it crossed the highway.