It was 1973, long before anyone could imagine hashtag declarations of solidarity and protest, the kind of message to the world that today might read, #IamCliffordGloverInTheFourthGrade.

No one could pull out a phone to make a video of Clifford Glover, a 10-year-old running from a plainclothes police officer with a gun who had just jumped out of a white Buick Skylark in Jamaica, Queens, on a spring morning in 1973.

“I am sure a camera would have helped, but the ballistics were clear,” Albert Gaudelli, a former Queens prosecutor, said this week. “The bullet entered his lower back and came out at the top of his chest. He was shot T-square in the back, with his body leaning forward. He was running away.”

That bullet killed Clifford Glover. Its trajectory — through a family, a neighborhood, a generation — can be traced to this day, in injuries that never healed, in a story with no final word. When a black man named Walter Scott was shot by a white police officer in North Charleston, S.C., on April 4, a cellphone video made by a passer-by showed that Mr. Scott was also running away when he was killed and that he was not, as the officer claimed, carrying a police Taser.