Can horses die instantly from hitting their head?

Don't watch the video if you're squeamish. The horse in stall 10 apparently panics in the gate, rears up and goes down.

The way a horse's poll is structured and the way a bone in the top of the head is a little "free" to move rather than being fixed means that if a horse hits the top of their head at a certain angle they can die - even from a mild injury. (Horses have died from being smacked on the head). It's just a weak point in what's normally a very, very solid protective structure.