On October 19, the eve of a traditional march to commemorate the 1944 Revolution, a death threat against 39 citizens was made by the self-proclaimed Anti-Communist Army (Ejército Secreto Anticomunista, ESA), a list including Oliverio Castañeda's name.
The march concluded without incidents in the Parque Centenario near the government palace (Palacio Nacional), where Castañeda gave a speech in which he pointed out violations to human rights involving state security forces.
Around 1 p.m., he and a group of students walked away from the park and when they crossed the Sexta Avenida, a major street of Guatemala City, one block away from the Palacio Nacional, several gunshots started, and a man got off a car opening fire with a machine gun against Castañeda.
The finishing shot was an evidence that Castañeda had been the victim of a deliberate attack, in the same context as other similar cases affecting student leaders, and was linked to a government speech accusing the USAC of subversive activity.
The impunity of this crime, and the lack of investigation from state authorities led the Guatemalan Historical Clarification Commission (Comisión para el Esclarecimiento Histórico, CEH) to consider Castañeda's death a violation of human rights, and to presume the Intelligence Division of the Estado Mayor Presidencial to be responsible for it.