Three years ago, HBO aired a documentary called “3 1/2 Minutes, Ten Bullets,” which examined the tortured aftermath of the death of Jordan Davis, a seventeen-year-old boy who was shot as he sat in an S.U.V. parked at a Florida gas station. At the start of the film, you see Lucy McBath, Davis’s mother, sitting at a table, depleted, telling how she came to name her son after the Biblical River Jordan. “I wanted to name him something that would symbolize the crossing over and a new beginning,” she says. Later, you see a more resolute McBath seated in a Senate hearing room with Sybrina Fulton—whose son Trayvon Martin was also shot to death at the age of seventeen—giving testimony about Stand Your Ground laws and their impact on her son’s death.