Headless Horseman

Since December 2009 I've always come into our office building and been confused by this massive artwork on the wall.  Rumor is that it is actually made from gold (but there are lots of rumors in China that I don't believe or even listen to).  However what really makes zero sense to me is that this has always been a "headless" horseman.  What happened to his head?

If you click on the photo you can get a bigger image of it and you will see that it almost looks like there was never a head on this man!