There's a world of difference in how you should treat someone you know almost nothing about that makes an mistake that is almost fatal for you and someone you know to be fairly responsible. That doesn't mean don't be nice if you can, relative to the situation ("nice" when someone has almost killed you doesn't necessarily mean be cordial, it may mean cool down for a sec before attempting to get them fired), but it would be stupid to assume the same mistake won't happen again without knowing a bit more about how it happened in the first place.