I thought I'd copy and paste the explanation Greg does give immediately below his video on You Tube on the day he posted it.
"!!! Be warned this video contains disturbing images !!!
I was not sure whether to put this video on YouTube or not, but here goes.
I was out stalking a couple of weeks ago when spotted a single roe deer on the ride. I watched it for a bit through binoculars, and knew there was something wrong with this deer as it was shaking its head, but it was too far to see, so I got closer. The deer was most of the time hidden in a dip and I could not get any closer than 100m. So I lay on the ground with my rifle on backpack in one hand and camera in another, hence video is a bit shaky.
It was a single roe kid in not the best shape (7kg clean) with a fresh head shot wound. The shot must have been taken side on and smashed the top of deer's head, but bottom jaw was intact. No one had been shooting this ground recently, so it must have been someone poaching or the deer came from a neighboring ground."
Hope this adds some information and clarification.