Wesley Lowery is a national reporter for The Washington Post and author of “They Can’t Kill Us All: Ferguson, Baltimore, and a New Era in America’s Racial Justice Movement.” Mamie Till-Mobley published “Death of Innocence” nearly 50 years after the murder of her 14-year-old son, Emmett Till. Her 2004 book, an account of Emmett’s life and death and the failure of justice in his killing, has served as a handbook for other families suffering a similar fate. “I quietly pray for the grieving mothers of other missing or murdered children,” Till-Mobley wrote. “We are connected, these other mothers and I. We share a bond, the knowledge of an exclusive few.” In February 2012, Sybrina Fulton and Tracy Martin gained that painful knowledge. Their son, 17-year-old Trayvon Martin, was shot and killed as he walked home from a convenience store in Sanford, Fla., a bag of Skittles in his hand and a can of Arizona iced tea in his pocket. His killer, George Zimmerman, was a self-appointed neighborhood watchman who found Trayvon suspicious. Zimmerman, armed with a gun, followed the boy, prompting a confrontation. After the shooting, Zimmerman claimed self-defense, and local police let him go. [A reporter on the front lines of police killings of African Americans] The nation’s eyes turned to Sanford as thousands demanded that Zimmerman be arrested and tried. “I am Trayvon” became a rallying cry painted on protest signs and posted online by athletes and celebrities. And later, after a jury declined to convict Zimmerman, the decision…more detail