José Calvo de la Hoz was on his way to the office of the Fiscal Service of the Port of Santurce, where he was stationed. He was sitting in his car, waiting to cross the Bilbao estuary on the transporter bridge connecting the Las Arenas district of Guecho with Portugalete.
Two ETA members, a man and a woman, walked up to the vehicle and opened fire. The sergeant was hit four times. He died shortly after being admitted to hospital.
This was the first ETA assassination following the end of a truce which had begun on 8 January 1989 to facilitate talks between ETA and the Spanish government in Algiers.