In 1975 Hausner was handpicked by Siegfried Haag to lead the group, known as Kommando Holger Meins who conducted the West German Embassy siege in Stockholm to force the release of 26 of his RAF comrades. Hausner was in charge of the wiring of the explosives. Twelve hours into the occupation, the explosives (15 kilogrammes of TNT) were apparently accidentally detonated.
In the documentary film Stockholm 75, fellow Kommando Holger Meins member Karl-Heinz Dellwo discussed the explosion and explained that only he and Siegfried Hausner were in a position near the detonator to trigger it and that he did not know why it exploded, only that he didn't activate it.
While fellow Kommando Holger Meins member Ulrich Wessel was killed instantly (the explosion causing him to drop a hand grenade), Hausner was severely wounded in the explosion, with burns to over 40% of his body and a fractured skull. Despite the recommendations of Swedish doctors, Hausner was immediately flown back to West Germany and hospitalized in Stammheim Prison, which had neither the equipment or specialist staff to treat severe burns. According to deputy chief prison officer Horst Bubeck, Hausner had "no chance of surviving, as the doctors saw immediately". He died on 5 May from a pulmonary edema.
His hurried relocation to Germany, the quality of treatment he received at Stammheim, and his subsequent death led many to blame both the West German government for killing him and the Swedish government for agreeing to his deportation despite being severely injured.
