The Margarita Belén Massacre took place during the Dirty War in Argentina. It involved the torture and execution of 22 Montoneros, some of whom were killed after surrendering and laying down their weapons near the town of Margarita Belén, Chaco Province, on 13 December 1976, in a joint operation of the Argentine Army and the Chaco Provincial Police. One of the victims of the massacre, Néstor Carlos Salas, is reported to have been a Montoneros commander and took part in a number of guerrilla operations. Argentina was at the time ruled by the National Reorganization Process.
The massacre was one of many cases included in the Trial of the Juntas in 1985, two years after the end of the dictatorship. The Buenos Aires Federal Chamber found junta leader General Jorge Rafael Videla guilty of homicide.
Wikipedia https://en.wikipedia.org/wiki/Margarita_Belén_massacre
Address Ruta Nacional 11, Argentina
Coordinates -27°6'57.401" N -58°58'9.278" E