That is a BJJ tournament, and that move would not be illegal, escaping from the guard that way is allowed - in BJJ the guard is considered a superior position. The guy with the broken back should have tapped out when he felt the strain on his back.
BJJ evolves around trying to isolate bodyparts and breaking them - that's kind of the whole point. When your opponent has a lock on you - you tap. If you don't tap out and as a result you end up with a broken arm or leg, or end up getting choked out you've only got yourself to blame. Never seen anybody actually have their back broken though.
b0und (former BJJ player)