On a chilly afternoon in south Georgia, more than 100 Transportation Security Administration trainees are huddled together on metal bleachers overlooking a field. They're watching an explosives instructor demonstrate what can happen if they don't do their job well.
"All right, confined smokeless powder in three, two, one."
The trainees (and an observing reporter) jump, startled by the explosion 100 yards or so before them.
More blasts follow, with different explosives. The lesson for these new hires? That the consequences of a mistake are deadly.