MEXICO CITY — Mexico’s student movement erupted so suddenly in the summer of 1968 that it seemed to catch even its followers by surprise.

The protests began as Mexico City was preparing to host the Olympics that October — an event intended to showcase a modern nation with a growing middle class at the forefront of emerging economies.

By taking to the streets just months before the inauguration of the games, students cracked that veneer, revealing a generation’s latent anger against the country’s repressive rule as the world looked on.

Ten weeks after the first street protests, the government crushed the movement in a spasm of violence beyond anyone’s worst fears. On Oct. 2, students who had gathered in a plaza for an evening meeting were picked off by government snipers perched on rooftops. Chaos broke out. The soldiers at the edge of the plaza, whose mission was to disperse the crowd, instead began to shoot into it.