That deer was NOT shot from a pen unless the acreage was in the thousands. Deer shot from pens have antlers that have little scratces all over them. Almost like they walked through a rosebush thicket. This comes from brushing their antlers on the fence. I know this because I have a buck and have seen bucks people have shot from pens.

That picture is really clear and there is no indication of a fence by looking at the rack of either deer. I say fair chase.