Three ETA members carrying pistols and submachine guns killed Unceta, the Government appointed President of the Provincial Deputation of Biscay and Mayor of Guernica.
The attack resembled the assassination of Juan María de Araluce Villar, the Government appointed President of the Provincial Deputation of Gipuzkoa, a year before.
[8] He had interests in local businesses and served as manager of Astra-Unceta y Cia SA, a large weapons manufacturing company founded by his father.
[8] His last official act before his death was in September 1977, when he participated in a memorial service for Juan María de Araluce Villar.
[5][14] In their claim of responsibility, ETA rejected this hypothesis, stating that, in their opinion, democracy had not been established in Spain and the country remained a military dictatorship.
[12] The assassination was condemned by all the main political parties on the left and right in Spain and the Spanish king and queen cancelled their attendance at a concert as a mark of respect.
[1] In August 2008, a street in Socuéllamos, the home town of Ángel Rivera Navarrón, one of the civil guards killed in the attack, was renamed in his memory.