The attack happened during the final months of the Nordic Biker War, a turf war fought between the Bandidos and Hells Angels for control of criminal rackets in Scandinavia and Finland, in which nine people had been killed prior to the bombing. The Bandidos had moved their headquarters from Oslo to Drammen the previous year. The bombing was ordered by Torkjell Alsaker, president of the Hells Angels in Norway, and was carried out by members of the Screwdrivers Motorcycle Club, an affiliated gang who were granted full membership to the Hells Angels as a result of the attack.