A few years back, I heard my dog yelping her 'scared' yelp and when I ran outside, a deer was chasing her. My dog saw me, ran towards me and up onto the deck behind me. I just stood my ground until the deer kept coming at me and then we both ran inside. I watched from the window as the deer turned and headed into the woods. She flipped up her tail and I saw blood on the white part (it was a big white-tailed deer). She'd VERY recently given birth! Not 5 minutes later, my boyfriend at the time spotted the fawn through the trees.

Anyway, since I now know that deer chase dogs and will even stand up to humans to protect their babies...I totally believe the deer was chasing the coyote in your yard! Good for her!