Dave,
Been there...somewhat. I've had that happen several times in past years. Deer cross my property to head into the neighbors cornfield but at times they stop to graze in what used to be my back yard. I don't mow it anymore as a yard but I brush hog it down a couple times each summer and they stop and graze on the natural forbes that have started to come back (curly dock, chicory, etc.) so we just wait until they move on to resume shooting. I've never had to quit shooting because they're there, but I've had to wait them out a few times.
BPS