"The one thread that was most surprising and most consistent was the lack of fear that people felt at the worst moment. They felt a lot of fear in early stages, when they're just realizing what's happening. But then things really seemed to be at their peak of terror, the fear went away. You can imagine why that's useful. At that moment your brain needs to focus all its attention on surviving, so people will feel a sense of calm as their brain tries to sort out a plan."