Cristina Mónica Illarmendi was killed while she was eating at the Rancho Chileno restaurant in Portugalete with her boyfriend Agustín Martínez and four of his colleagues. For some time, they had been in the habit of having lunch at the same restaurant. Four unmasked terrorists from the Vizcaya Unit of ETA burst into the premises and fired several bursts of machine-gun fire at the table where Agustín, his girlfriend Cristina and four National Police officers were sitting. Agustin and Cristina were killed instantly, and the other three inspectors were injured. Officer Alfonso Maside Bouzo died almost immediately afterwards.
One of the police returned fire from the ground, and succeeded in wounding ETA member Enrique Letona in the leg, although he eventually got away with his accomplices. Police later retrieved around a hundred cartridge cases from the scene of the crime.