They waited more than 50 years to put on their caps and gowns: That rite of passage had been denied to the members of the Class of 1970 at what is now Jackson State University in Mississippi, after a deadly police shooting at the historically Black college that spring brought their college years to an abrupt end.

Their graduation was canceled.

But on Saturday, the group of more than 400 former students had the chance to hear their names called and to walk across a stage.

They received more than their diplomas: City and state officials apologized for the violence that had claimed the lives of two people and wounded a dozen others after local police and state highway patrol officers opened fire while responding to campus protests over racial injustice on the night of May 14, 1970.

Mayor Chokwe Antar Lumumba of Jackson said during the ceremony that it was long overdue for the city to accept responsibility for the bloodshed.

“As James Baldwin once wrote, ‘When we cannot tell the truth about our past, we become trapped in it,’” Mr. Lumumba said, referring to the Harlem-raised author. “I believe as a city we must publicly atone for the sins of our past and proclaim a new identity of dignity, equity and justice.”

Tensions over racial discrimination had been escalating at the university, which was called Jackson State College at the time, when officers descended on the campus on that night. A dump truck had been set ablaze on a nearby street, drawing a phalanx of heavily armed officers to the campus and an armored police vehicle.

The situation grew worse as it got closer to midnight.

In the early hours of May 15, protesters threw rocks and pieces of bricks, though no serious injuries to the police were reported, according to a report by the President’s Commission on Campus Unrest issued later that year.

Claiming that a sniper had fired at them from a women’s dormitory (a claim that was never substantiated), the officers sprayed the area with nearly 400 rounds, the report said.