I had to do the same thing last fall. Bunch of young men in a compact car hit it, they tried but couldn't finish it off. I covered its eyes and pet it little and it calmed right down, didn't care what the sex was....... just wanted the deer to be out of its misery, 3 legs broke and a whole lot of damage to the rib section. The yearling didn't have a chance, hopefully its spirit will live on.
When I see the real young fawns while walking the dog they usually don't run until your right on top of them, I would think that w/farm machinery they wouldn't have enough time to get away.