I have only one encounter that I could relate with a coyote. This was about 3 or 4 years ago and occurred right at dark. I was walking back to the truck after legal hunting arrows were over when I happened to walk past a thick stand of pines. As I was walking past I heard a low groooowwwlll sound. I turned to look and noticed the coyote silhouetted against the ligtened sky on the other side of the pines. I didn't waste time and continued to walk towards the truck though the coyote never moved from his original spot.

I didn't really interpet that as aggressive but rather that he was just letting me know he was there.