Sometimes, no matter how well you coach, manage, and possibly even baby your client, a public relations disaster happens. Sometimes they're just unavoidable – a plan crashing, a celebrity using your product in the commission of a felony, Congress grilling you on CSPAN because your industry, or a natural disaster. What do you do when no amount of foresight and planning could have made the disaster avoidable?
It does not matter if you're at fault or not, people respond to apologies. That does not mean yo should take the blame, especially if you're not at fault or if there's some gray area in passing out blame, but expressing remorse is never a bad thing and could get you some good will down the line.
Also, this apology should take place as soon as possible. Waiting too long makes it look like your hand was forced instead of looking like a reasonable response to the situation. Do not give people the chance to think you're only apologizing as a public relations move instead of because you really care.
Look Into the Matter
Depending on the disaster a government agency may already be looking into the matter, but the presence of the Alphabet Squad should not preclude you from running your own investigation into the matter. Was this really an unavoidable incident, or should you have seen this coming from a mile away? Was there something, within reason, that your company could have done to prevent it, or was this a really unavoidable incident that was going to happen regardless of what you did outside your control?
Finding out the answers to these questions before the media does can do a lot to mitigate the public relations nightmare. If there was something you could have done, admitting it and correcting the problem can go a long way towards engendering public support by showing that you're ready to admit your mistakes and proactively fix the problems.
Time Heals All Wounds
No matter how preventable or how well handled the moment is, somebody will still hold it against you. That is, unfortunately, the way of the world. That being said, time really does heal all wounds. Make your apologies, change what needs to be changed, and then just give it some time. The public will actually forgive you, or at the least, shift their ire to somebody else when the next relations relationship disaster for somebody else comes to their attention.