Another good HBR article, this one on dealing with crises: https://goo.gl/hqZDDi

Remember that as the CEO/leader, you set the tone for your organization’s conduct in, and response to, crises. People will look to you to set an example. If you appear emotional and stressed, so will they. Conversely, if you can control your emotions and project an image of confidence and calm, they are far more likely to do so as well (and other stakeholders will be more assured). I often come back to the analogy of the swan: it always appears calm and regal on the surface, even if it is flapping like mad below the waterline.

One other point: Make sure you are visible in a major crisis. Let people know that you are taking it seriously and that you are providing decisive leadership and direction.