Apparently the cyclist featured in this video is mountain biker Evan Van Der Spuy who was taking part in a race at Albert Falls Dam, South Africa.
His team mate, Travis Walker, who was following behind filmed the entire incident courtesy of a camera mounted on his handlebars. You can clearly see that Evan spots the Hartebeest racing towards him just before the animal leaps into the air and slams him to the ground. Thankfully he managed to escape relatively undamaged which is more than can be said for his helmet, which saved his life.
Mountain biking in South Africa is obviously different gravy.