can't say if the buck is real or not but if he faked it he did it in a hurry. The buck in the video has not been gutted and shows no signs of rigor mortis because he lifts the head and the neck bends its not stiff.
You realize the rigor mortis only lasts for a short period of time, right? Rigor mortis comes and then goes away. It normally doesn't last more than 24 hours. So the fact that the buck didn't have rigor mortis means absolutely nothing. Second, the time portion of pulling off a scam like this would have been making the horns. The rest would fall into place in very short order. Five minutes would be more than enough time!