Hi, bongowwf, I still think it is not a Gongshan muntjac, and as its antlers are so short, it is not a Reeve's muntjac. But I also haven't seen a black muntjac like this..... Maybe hybrid?
The black muntjac has absolutely black body. The Black Muntjac
You cannot see the size on the picture, but this animal was much bigger then reeve's muntjac.
I just uploaded a photo showing a size comparison between this animal and a Reeves' muntjac (this one is sitting down and the Reeves' is standing, but the difference is obvious). http://www.zoochat.com/1686/muntjacs-339661/
