well, we can't really see what happened because they are showing a vantage point from where it happened. If you look at the bike there are skid marks moving away from the body, showing you that the bike went further than he did, which leads you to believe he himself hit something instead of the bike hitting something and throwing him off, because if the bike hit something it wouldn't have went as far as it did. we can;t really tell what happened without seeing the other way down the road
edit: looking at it again it looks like he might have hit the wall because there is a blood? stain consistant with the scrapes the bike made that are moving away from the wall. maybe he almost hit the pole, swerved right, hit the rock wall, and got severed? but that wouldn't throw his shoe backwards like in the picture. who knows, you can't really tell without seeing the other side of the pictures