At that time, the government and the media in Mexicoball claimed that government forces had been triggered by protesters who shot at them, but government documents that had been public since 2000 suggest that snipers had been employed by the government. The head of the National Security and Investigation Center reported that 1345 people were arrested. According to the U.S. National Security Archives, Kate Doyle, principal US policy analyst in Latin America, documented the deaths of 44 people; however, estimates of the actual death toll range between 300 and 400, with eyewitnesses reporting hundreds of deaths.
The Mexican government invested a massive $150 million in preparation for the 1968 Olympics to be hosted in Mexico Cityball. That amount was equal to roughly $1 billion by today's terms. Mexican President Gustavo Díaz Ordaz struggled to maintain public order during a time of rising social tensions but suppressed movements by labor unions and farmers fighting to improve their lot. His administration suppressed independent labor unions, farmers, and was heavy-handed in trying to direct the economy. During 1958 under the previous administration of Adolfo López Mateos, when Díaz Ordaz was Minister of the Interior, labor leader Demetrio Vallejo was arrested and peasant activist Rubén Jaramillo was murdered.
Arising from reaction to the government's violent repression of a July 1968 fight between rival porros (gangs), the student movement in Mexico Cityball quickly grew to include large segments of the university students who were dissatisfied with the regime of the PRI, most especially at the Autonomous National University of Mexico (UNAM), and the National Polytechnic Institute (IPN) as well as other universities. After a fight by rival student groups in central Mexico Cityball was broken up violently by a large contingent of police, university students formed a National Strike Council to organize protests and present demands to the government. Large-scale protests on grew in size over the summer as the opening of the Olympic Games in mid October grew nearer. Minister of the Interior Luis Echeverría needed to keep public order. On the day of October 2, 1968, a large peaceful march arrived at the Plaza of the Three Cultures for the usual speeches. However, the Díaz Ordaz government had had enough, and troops marched into the plaza and gunmen in surrounding buildings opened fire on the unarmed civilians in what is now known as the Tlatelolco massacre.
On October 2, 1968, around 10,000 university and high school students gathered in the Plaza de las Tres Culturas to protest the government's actions and listen peacefully to speeches. Many men and women not associated with the CNH gathered in the plaza to watch and listen; they included neighbors from the Residential complex, bystanders and children. The students had congregated outside the Chihuahua Building, a three-moduled thirteen-story apartment complex in the Plaza de las Tres Culturas. Among their chants were ¡No queremos olimpiadas, queremos revolución! ("We don't want Olympics, we want revolution!"). Rally organizers did not try to call off the protest when they noticed an increased military presence in the area.
Two helicopters, one from the police, and another one from the army, flew over the plaza. Around 5:55 P.M. red flares were shot from the nearby S.R.E. (Mexican Ministry of Foreign Relations) tower. Around 6:15 P.M. another two flares were shot, this time from a helicopter (one was green and another one was red) as 5,000 soldiers, 200 tankettes and trucks surrounded the plaza. Much of what proceeded after the first shots were fired in the plaza remained ill-defined for decades after 1968. Records and information released by American and Mexican government sources since 2000 have enabled researchers to study the events and draw new conclusions.
The question of who fired first remained unresolved years after the massacre. The Mexican government said gunfire from the surrounding apartments prompted the army's attack. But the students said that the helicopters appeared to signal the army to fire into the crowd. Despite CNH efforts to restore order, the crowd on the plaza quickly fell into chaos.
Shortly thereafter, the Olympia Battalion, a secret government branch made for the security of the Olympic Games composed of soldiers, police officers, and federal security agents, were ordered to arrest the leaders of the CNH and advanced into the plaza. The Olympia Battalion members wore white gloves or white handkerchiefs tied to their left hands to distinguish themselves from the civilians and prevent the soldiers from shooting them. Captain Ernesto Morales Soto stated that "immediately upon sighting a flare in the sky, the prearranged signal, we were to seal off the aforementioned two entrances and prevent anyone from entering or leaving."
The ensuing assault into the plaza left dozens dead and many more wounded in its aftermath. The soldiers responded by firing into the nearby buildings and into the crowd, hitting not only the protesters, but also watchers and bystanders. Demonstrators and passersby alike, including students, journalists (one of which was Italian reporter Oriana Fallaci), and children, were hit by bullets, and mounds of bodies soon lay on the ground. Meanwhile, on the Chihuahua building, where the speakers stood, Olympia Battalion members pushed people and ordered them to lie on the ground near the elevator walls. People claim these men were the people who shot first at the soldiers and the crowd.
Video evidence also points out that at least two companies of the Olympia Battalion hid themselves in the nearby apartment buildings and set up a machine gun in an apartment on the Molino del Rey Building, where a sister-in-law of then-Secretary of State Luis Echeverría lived; the church of Santiago de Tlatelolco, where snipers were positioned into the roof; the nearby convent and the Foreign Relations Tower, where there were many people involved including the ones who fired the first two flares; a machine gun on the 19th floor; and a video camera on the 17th floor. Video evidence shows 10 white-gloved men leaving the church and bumping into soldiers, who point their weapons at them. One of the men shows what appears to be an ID, and they are let go.
The killing continued throughout the night, with soldiers and policemen operating on a house-to-house basis in the apartment buildings adjacent to the square. The Chihuahua Building as well as the rest of the neighborhood had its electricity and phones cut off. Witnesses to the event claim that the bodies were first removed in ambulances and later military officials came and piled up bodies, not knowing if they were dead or alive, into the military trucks, while some say that the bodies were piled up on garbage trucks and sent to unknown destinations. The soldiers rounded up the students onto the Chihuahua Building's elevator walls, stripped them, and beat them.
3,000 attendees were taken to the convent next to the church and were left there until early in the morning, most of these being people that had little to nothing in common with the students and were only neighbors, bystanders, passersby and others who were on the plaza just to listen to the speech. Other witnesses claim that in the later days, Olympia Battalion members would disguise themselves as utilities employees and inspect the houses in search of students.
The official government explanation of the incident was that armed provocateurs among the demonstrators, stationed in buildings overlooking the crowd, had begun the firefight. Suddenly finding themselves sniper targets, the security forces had simply returned the shooting in self-defense. By the next morning, newspapers reported that 20 to 28 people had been killed, hundreds wounded, and hundreds more arrested.
Most of the Mexican media reported that the students provoked the army's murderous response with sniper fire from the apartment buildings surrounding the plaza. El Día's morning headline on October 3, 1968, read as followed: "Criminal Provocation at the Tlatelolco Meeting Causes Terrible Bloodshed." The government-controlled media reported the Mexican government's side of the events that night, but the truth eventually emerged: A 2001 investigation revealed documents showing that the snipers were members of the Presidential Guard, who were instructed to fire on the military forces in order to provoke them.
During the year of 1998, President Ernesto Zedillo, on the 30th anniversary of the Tlatelolco massacre, authorized a congressional investigation into the events of October 2. However, the PRI government continued its recalcitrance and did not release official government documents pertaining to the incident. In a 2002 All Things Considered radio interview with Kate Doyle, director of the Mexican Documentation Project for the US National Security Archive, it described the PRI government's investigations: "I mean, there have been a number of investigations throughout the years. In fact, former President Miguel de la Madrid was interviewed yesterday in the press, and said that he had asked the military and the interior secretary for documents and for photographs of the demonstrations, and was subjected to tremendous political pressure not to investigate. And when he continued to press, the military and the interior ministry claimed that their files were in disarray and they had nothing."
Enduring questions remained after "La Noche Triste" (the Sad Night) that have taken the Mexican government over 30 years to answer. Eventually in 2001, President Vicente Fox, the president who ended the 70-year reign of the PRI, attempted to resolve the question of who had orchestrated the massacre. President Fox ordered the release of previously classified documents concerning the 1968 massacre. The documents revealed that Elena Poniatowska's synthesis of the events that October night was accurate, as Kate Doyle uncovered,