It was a typical evening at a mall outside Portland, Maine. Three teenage friends waited for the movie to start. A boy flirted with the girl selling sunglasses. Mothers and children shopped together, and the manager at the video-game store tending to customers. Then the shooters arrived. The chaos and carnage lasted only eight minutes before the killers were taken down. But for those who lived through it, the effects would last forever. In the years...