When university students in Mexico City protested the government's actions around the time of the 1968 Summer Olympics, Díaz Ordaz oversaw the occupation of the National Autonomous University of Mexico and the arrest of several students, leading to the shooting of hundreds of unarmed protesters during the Tlatelolco massacre in Downtown Mexico City on 2 October 1968. The Mexican army fired ruthlessly because a group called "Battalion Olympia" started the shooting between the unarmed students and many other people who let the students take shelter inside their homes. Statistics concerning the casualties of this incident vary, often for political reasons. Some people were kept imprisoned for several years. The crackdown would eventually be denounced by Díaz Ordaz's successors, and ordinary Mexicans view the assault on unarmed students as an atrocity. The stain would remain on the PRI for many years.