Sergeant Jerónimo Vera García and another officer were taking part in a joint investigation by the Civil Guard and the National Police into ETA activities. The operation came a month and a half after the group had committed its first massacre at the Café Rolando in Calle Correos in Madrid.
The Civil Guard had received information that a member of the terrorist organisation was in the Trincherpe district of San Sebastián. At around 7.30 pm, the two officers went to the neighbourhood to verify the information. They stopped an individual and asked for his papers. At that moment, ETA member Ignacio Iparraguirre Aseguinolaza pulled out a pistol and fired at Sergeant Vera. He was wounded in the chest and died shortly afterwards at the military hospital in San Sebastián.