The shooter who killed 18 people with an assault-style rifle in Lewiston, Maine, displayed a textbook set of warning signs: He was hearing voices. He told people that he was planning violence. And his behavior had markedly changed in the months leading up to the mass shooting he carried out last month. His family, his superiors in the military and the local police knew all of this. Yet no one stopped him. #lewistonmaine Video by Shaila Dewan and Claire Hogan