We are gathered here today not to argue about some policy prescription, nor to excoriate some public figure. No, we are gathered because sometimes, you have no choice, sometimes, you simply have a duty to bear witness.

A child was killed last week in Chicago. He was shot to death.

It is a measure of America that the statement is, of itself, unremarkable. Children are shot all the time in this country. But what makes this shooting stand out is that 9-year-old Tyshawn Lee was targeted. Police say the child, who was black, was lured into an alley and shot multiple times.

According to them, the execution was part of an ongoing dispute between rival street gangs and was intended as retaliation against Tyshawn’s father, Pierre Stokes. They say Stokes, 25, is a gang member who has refused to cooperate with the investigation. Stokes, in turn, told the Chicago Tribune he doesn’t believe the killing had anything to do with him and that anybody who wanted to hurt him could do so easily enough without going after his son. “I’m not hard to find,” he said.

Twenty-one years ago, a 5-year-old black child named Eric Morse was dropped 14 stories to his death by a 10-year-old and an 11-year-old because he would not steal candy for them.

It is, however, the death of another black boy from Chicago that paints all this in shades of irony. In 1955, Mamie Till Mobley sent her 14-year-old only child, Emmett Till, down South to spend the summer. After he was lynched for supposedly flirting with a white woman, she recalled ruefully how she had warned him to be careful; told him Mississippi was dangerous for black children.

But six decades later, there are few places more dangerous for black children — for black people — than Chicago itself. In 2014, 411 people died there by murder or non-negligent manslaughter. New York City, with three times Chicago’s 2.7 million population, only recorded 333 such deaths. An overwhelming number of the victims were (as always) African-American.

Black lives matter, we say. Indeed, a lifetime ago, black people decided they mattered too much to sit helplessly by as they were poured out like water by hateful white men in places like Mississippi, Florida and Arkansas. So six million strong, they fled the South in a Great Migration, seeking “liberty and justice for all,” “all men are created equal,” “life, liberty and the pursuit of happiness” and all the other promises that comprise America.

Chicago was one of their major destinations. It was the pot of gold at the end of the railroad tracks. It was the exhalation of hope heard as the bus doors sighed open.

But black people soon found that in Chicago — as in other cities — America’s promise offered them only mop buckets, chauffeur’s caps and ghettos teeming with vermin, the constricted parameters of their lives patrolled by police with batons and bankers with maps crisscrossed by red lines. Eventually, the parameters would also enforce themselves: miseducation, teen pregnancy and crime.

Small wonder, in that sludge of human malfunction, that someone became cold enough to target a little boy for execution. Or that a 25-year-old father now mourns a 9-year-old son.

And bearing witness feels like impotence, but like duty, too, a reminder that there are promises America still owes African America, and that African America also owes itself, promises life owes to life and that the price of the ongoing refusal to keep those promises is too often paid in children’s blood.

Five days after Tyshawn’s murder, a boy named J’Quantae Riles was shot to death shortly after visiting a Chicago barbershop. He was 14.

Leonard Pitts is a columnist for The Miami Herald, 1 Herald Plaza, Miami, Fla., 33132. Readers may contact him via e-mail at lpitts@miamiherald.com.