23 April 1937,
Eibar was bombed by Francoist aviation. In the bombing there were two deaths. On the same day, Franco bombed the urban centers of Barakaldo, Bilbao, Elgeta and Erandio, as well as other positions bombed for tactical purposes. Three days later, Eibar fell into the hands of the franchises.
Source:
Xabier Irujo, Atlas of Bombardments in the Basque Country (1936-1937) (Memory Collection).