On the morning of 11 December 1987, the Argala unit of ETA militar parked a car containing 250 kilograms of ammonal at a side entrance to the Guardia Civil Barracks on Avenida Cataluña in Zaragoza. At 6.10 am, terrorist Henri Parot alighted from the stolen vehicle, activated the detonator by remote control and fled the scene.
The officers on duty in the security hut suspected that it was an attack. One of them chased after the ETA member, who got into a wating getaway car. The other went up to the apartments to warn an explosives expert but did not get there in time. The bomb exploded in the block, inhabited by some 40 families of civil guards and children of officers from other parts of Spain who were studying to enter the academy.
The building collapsed and the explosion left a hole measuring over 10 metres in the wall. The blast also damaged nearby homes. Eleven people, including six minors, were killed instantly and a further 88 were injured.
Pedro Ángel Alcaraz Martos, a 17-year-old student of hairdressing, was one of those killed. He lived with his older sister Rosa, who was married to a civil guard and their two 3-year-old daughters. The girls were also killed in the attack.