It was perpetrated with a bomb by two men from OAS and UDR movements, in a context of resurgence of far-right violence in France.

On 9 May 1970, at 10:30 pm, the place du Huit-Septembre (September 8 Square) was shaken by an explosion.

[1] Damage was substantial but limited : only the porch, the bay windows, and the salle des pas perdus (hall of lost steps), partly classifieds, were seriously affected.

[1] The mayor, the socialist Jean Minjoz, immediately condemned this act, while the investigation began.

[1] At first the attack was attributed to the left[3][4][5] but two individuals were arrested on 14 May with the number of their a registration plate.