Your disappointed- that's understandable. However he didn't do it on purpose- it was an accident. You lost 4 hours- not ideal but not the end of the world.

It's a game it's supposed to be fun! He was trying to have fun too but it ended up ruining your expectations for the game. You need to reevaluate your expectations. Things happen. Does it stuck you need to start over? Sure. But is it really- in the big scheme of things something that should ruin your day? His day?

Saying he can no longer play your Xbox and being this upset is an overreaction to an accident. I think you need to take a step back and look at the situation rationally. It's a game. It's not a real animal. It wasn't done maliciously. You Can go back and fix the issue. It's a minor inconvenience that you've made a major one..I personally think you should apologize.