It's amazing how many companies still don't get it.

You made a very public mistake -- apologize, wholeheartedly and genuinely, and accept responsibility. That's it!

Making it seem like it's not a big deal makes it come off defensive, unprofessional, and like an excuse..

Now is not that time for that -- use the mitigating details in a follow-up post that highlights your progress and what you've implemented to ensure it never happens again. Don't do it now.