Sybrina Fulton was thrust into the national spotlight more than a decade ago for the worst possible reason: her son, Trayvon Martin—an unarmed teen-age boy returning from the store—was shot. Her son’s body was tested for drugs and alcohol, but not the self-appointed neighborhood watchman, George Zimmerman, who killed him, claimed self-defense, and was acquitted. “Trayvon Martin could have been anybody’s son at seventeen,” Fulton tells David Remnick. He was an affectionate “mama’s boy” who wound up inspiring a landmark civil-rights movement: Black Lives Matter. B.L.M. became a cultural touchstone and a political lightning rod, but all its efforts can’t make Fulton whole again. “I think I’m going to be recovering from his death the rest of my life,” she says. “It’s so unnatural to bury a child,” she says. Fulton has become an activist and founded Circle of Mothers, which hosts a gathering for mothers who have lost children or other family members to gun violence.