On the night of 25 September 1985, José Sabino Echaide Ibarguren, Ignacio María Astiasuinzarra Pagola, José María Echaniz Maiztegui and José Agustín Irazustabarrena Uruzola were having a drink in the bar of the hotel Monbar in Bayonne (France), which was frequented by sympathisers of the Basque nationalist left and ETA members. Around 9.15 pm, when they were standing at the bar, two individuals got out of a car and entered the premises armed with machine guns. One of the terrorists stayed at the door to make sure nobody left the establishment while the other fired a number of rounds at the heads and chests of the customers.
Echaide, Astiasuinzarra, Echaniz and Irazustabarrena were killed and a fifth man, a French citizen, was seriously injured. Several witnesses chased the assailants on foot and managed to detain them until the French police arrived. The two men were mercenaries, with links to the Marseilles criminal underworld, who had been hired by GAL.
José Sabino Echaide Ibarguren, known as Sabino Etxaide, alias Eskumotza, had been living in the French Basque Country for three years. He had been arrested in 1979 and charged with being part of an ETA militar information unit. He was shot in the brain and was the only one of the four not to die instantly. He died two hours after the attack while undergoing surgery.