Yes, I and the person who reviewed the change bear more responsibility than the new developer. Also, I say "new guy", but the person who had interned with us the Summer after "the new guy" had already joined full time at that point, so "the new guy" had been working full time with the team for at least 9 months at that point. I also remember the room where it happened, which wasn't the first room we were in, so maybe he had been with us full time more like 18 months. In any case, it was the first time when he was trying keep the weight of billions of dollars out of his head and calmly but quickly fix a bug.
That's impractical in organizations with flatter structures and general purpose communication channels.
What would you suggest, kicking everyone off of internal IRC/Slack/mailing lists/etc.?
Edit: if you are managing someone who is new in a job, it's your job to make sure they don't push bugs to break important stuff in the first place.