On October 2, 1968, soldiers and police in Mexico City fired into a crowd of students and their families in the Plaza de las Tres Culturas at Tlatelolco, a few hours after the demonstration began. The government said four people had been killed. The figures established since, from declassified files and from investigations in the 1990s and 2000s, run between 300 and 400 dead, many of them shot in the back or inside the buildings where they took refuge. Nobody has ever been convicted.
The protest was the last of a movement running since July, when police had broken up a fight between students of two vocational schools with armoured cars and a bazooka and then occupied the campus of the National Autonomous University. The movement demanded the repeal of the law against social dissolution, the release of political prisoners and the removal of the police chief. It had held a silent march of 60,000 in September.
The government of Gustavo Diaz Ordaz was ten days from hosting the Olympic Games, which had cost the country a large share of its budget and which the president intended as a showcase of Mexican modernity. The organising committee had publicly said the games might be cancelled. What the government did instead was put the army and the presidential guard into the square beforehand, in civilian clothes, with orders to arrest the speakers on the balcony of the Chihuahua building.
The shooting started at about six in the evening, once the speakers had been taken. It continued for hours. About 5,000 soldiers and 300 police were involved. Witnesses, including those Elena Poniatowska interviewed for her 1971 book, described soldiers firing from the surrounding buildings into the crowd and then searching the flats afterwards. The government's own documents, opened in 1998, name 44 dead within a day.
The games went ahead. Those Olympics are remembered for the Black Power salute on the podium and for Bob Beamon's long jump, and the massacre that preceded them was not publicly acknowledged by the Mexican state until 1998. A special prosecutor was appointed in 2001 and indicted Luis Echeverria, interior minister at the time, in 2006. The charges were dismissed in 2009 for lack of evidence.