The late 1960s were a time of political unrest in Mexico and many western nations. On October 2, 1968, ten days before the start of the 1968 Summer Olympics, the plaza was the scene of the Tlatelolco massacre. The exact number of dead and injured in that tragic afternoon is still unknown, but it is estimated that 15 thousand shells were fired and there were more than 300 dead and 700 injured by the Mexican army and police who were trying to suppress the protests, in addition, 5 thousand students were arrested.