At 8.45 am on 29 September 1975, five members of a terrorist unit killed police officer Diego del Río Martín during a raid on the cashier’s office of the Valle de Hebrón Hospital in Barcelona. The assailants mingled with staff who were queuing to pick up their pay packets. They then fired on Diego del Río Martín and his fellow officer, who were on guard duty, with pistols and machine guns. The assailants made off with money from the payroll. Diego del Río Martín died from his injuries. His colleague, Enrique Camacho Jiménez, managed to survive.
Most sources believe that the attack was perpetrated by the First of October Anti-Fascist Resistance Groups (GRAPO), but others suggest that it may have been the work of FRAP or EPOCA.