I'm sorry for your loss. I can imagine how upset you are.
I have a couple of English Setters, both females. The older of the two seems to like to run with deer. A couple of times she has seen groups of five to eight and she took off into the woods with them. She is fast and cannot be outrun by a deer -- she got out of my sight both times and I could hear her deep in the woods yelp from time to time. She came back both times, happy, with a smile on her face and not hurt. Not seeing what was going on, I just figured she got tangled up in some deer legs during the run, but now I wonder if the deer turned on her and chased her out of the woods.
Bruce