Domingo Merino Arévalo was a 28-year-old travelling salesman who was killed by ETA on 5 July 1978 when he was parking his car at the Duque Hotel in Zarauz. He was shot six times at close range. Initially, it was thought that Domingo Merino, who had many close friends in left-wing Basque nationalist circles, had been killed by members of a far-right organisation. However, the next day ETA took responsibility for the attack, claiming that the victim had very close ties to the Civil Guard and that they had information that he was trying to get close to left-wing Basque nationalist circles in order to pass information to the security forces.
Domingo was from Ciudad Real, although he had been living in the Basque Country for eight years. At the time of his death, he was separated from his wife. Their son, Óscar Villafañe, was bereaved twice by ETA; the group also killed his maternal grandfather, Juvenal Villafañe, on 16 September 1975.