Really awful. I remember seeing the footage of Clint Malarchuk getting the same injury in an NHL game. You literally see blood spurting into the air with each beat of his heart. Luckily for Malarchuk, his team's physio was a former combat medic and he survived, but suffered from PTSD.
Neck guards will be made mandatory now and, they probably already should've been. These injuries are rare in hockey, but not unheard of. It's not deliberate. No hockey player would do that. However, it's clumsy and irresponsible. You have a responsibility not to put yourself in a situation where a missed hip check will result in your skates flying up at head height.