Forty-three years later, it remains a grisly benchmark: Aside from the Indian massacres of the late 19th century and an infamous 1921 race riot in Tulsa, the State Police assault that quelled the four-day uprising at Attica prison in upstate New York in 1971 was, investigators concluded, “the bloodiest one-day encounter between Americans since the Civil War.”

When it ended, 10 correction officers and civilian employees and 33 prisoners were dead — all but one guard and three inmates killed in what a prosecutor branded a wanton “turkey shoot” by state troopers.

Prosecutions stemming from the uprising were resolved long ago; scores of inmates and one state trooper were charged. Civil suits by relatives of the dead and injured were settled (the state paid $12 million, including legal fees, to families of the inmates, and another $12 million to families of prison employees).