regular runs near the Casco de Santo Tomás (one of the IPN's main campuses). June 10 The march started at the Casco de Santo Tomás, and proceeded through Carpio and Maestros Avenues so the protesters could take the Mexico-Tacuba Causeway, and eventually end up at Zócalo. The streets leading to the Maestros Avenue were blocked by police officers and riot police, who did not allow the students to pass. There were tankettes parked along Melchor Ocampo Avenue, near the military school, and riot police trucks in a large police contingent at the intersection of the Melchor Ocampo and San Cosme avenues. A shock group trained by the Federal Security Directorate and the CIA, known as "los Halcones", who came in grey trucks, vans, and riot trucks, attacked students from streets near Maestros Avenue after the riot police opened their blockade. The shock group first attacked with bamboo and kendo sticks so the students easily repelled them. Los Halcones then attacked the students again, with high-caliber rifles, while students tried, unsuccessfully, to hide. The police did not intervene because they had been ordered not to. The shooting lasted for several minutes, during which some cars gave logistical support to the paramilitary group. The support included extra weapons and makeshift transports, such as civilian cars, vans, police vehicles and an ambulance from the Cruz Verde (an organization similar to the Red Cross). The injured were taken to the general hospital Rubén Leñero, but to no avail, as the Halcones reached the hospital and killed them, while many were still in the operating room, and took the opportunity to scare the inmates. Nearly 120 protesters were killed, among them a fourteen-year-old boy. That night army elements guarded the National Palace and Luis Echeverría announced an investigation into the killing and said he would punish the guilty. Alfonso Martínez Domínguez, then-Mexico City governor, and , attorney general, denied that there were Halcones and police chief Escobar blamed the students for creating extremist groups within their movement. A week passed before Escobar accepted that there were Halcones, but denied their involvement in the massacre. The high number of journalists and photographers hit and arrested by Halcones managed to contradict the government's official version. Martínez Domínguez tendered his resignation on June 15 to Echeverría because he was convinced that the protesters had been provoked, among other things, so the government had an excuse to get rid