This event occurred during the early months of the Spanish Civil War, when the city was already under the control of the rebel forces, who received military assistance from Germany and Italy. As part of this support, German planes and pilots arrived in Vitoria to reinforce the Francoist side. Among them were six Heinkel HE51A biplane fighters, used for combat and patrol missions.

On Monday, September 28, the Heinkel squadron took off at eight in the morning for a mission outside the city. As they flew over Vitoria-Gasteiz, the planes entered the city center via Postas Street, flying over buildings. According to accounts, 2nd Lieutenant Ekhehard Hefter broke formation and approached the vertical of Plaza España to drop a bouquet of flowers, in gratitude to the municipal authorities for the hospitality the city had shown the pilots. This action, however, would end in tragedy.

For reasons that have not been definitively determined (mechanical failure, maneuver error, or collision with a tree, antenna, or cable), the plane lost control and crashed in the square. Upon impact with the ground, the aircraft caught fire, and the flames caused the ammunition it carried on board to detonate. The toll was devastating: three people died, the German pilot and two civilians. Antonio Peral Maza, who sold milk in the square, died instantly, while Vicente Julio López de Lacalle Erauskin, a young blacksmith from Maeztu, died from severe burns.

The incident was virtually invisible in the press and official records due to Francoist censorship. Today, we know about this accident thanks to photographs by José María Knörr Elorza and witness accounts. Knörr took the photos to be developed by the Vitoria photographer Alberto Shommer Koch, who, defying orders to hand over any images of the accident to the police, gave them to Knörr, who kept them secret until 2004.

That year, the images were published in Pedro Morales Moya's book Recuerdos de Vitoria - Mis conversaciones con José María Knörr, also based on the work of Óscar Bruño Royo published in September 2000. Finally, in September 2018, Vitoria-Gasteiz placed a commemorative plaque in the Plaza Nueva, remembering the deceased residents and honoring their memory. Today, that spot has become a place of remembrance for the two civilian victims of that tragic accident.