Things will go wrong. Even if you have great deployment processes, good test coverage and QA, there will be issues.
Hopefully you'll catch them before they hit production, but they may still make coworkers unproductive and irritated when you check in some piece of crud which breaks all other scenarios than the happy path you were dealing with.
The first thing to do is to assign blame.
Why? It is so human to do so, everybody does it so get it done right away.
It is also very unproductive to spend time assigning blame when time should be spent fixing whatever it is and then making it very unlikely to happen again. Sometimes it's an all hands on deck scenario and if someone is focused on avoiding blame - or assigning blame - they are not being helpful.