1977 Atocha massacre

The 1977 Atocha massacre was an attack by right-wing extremists in the center of Madrid on 24 January 1977, which saw the assassination of five labor activists from the Communist Party of Spain and the workers' federation Comisiones Obreras. The act occurred within the wider context of far-right reaction to Spain's transition to constitutional democracy following the death of dictator Francisco Franco. Intended to provoke a violent left-wing response that would provide legitimacy for a subsequent right-wing counter coup d'état, the massacre had an immediate opposite effect, generating mass popular revulsion of the far-right and accelerating the legalization of the long-banned Communist Party.

On the evening of 24 January, three men entered a legal support office for workers run by the PCE on Atocha Street in central Madrid, and opened fire on all present.

Source: Wikipedia