Although living in East Berlin, he was in West Berlin when the Berlin Wall was built in 1961, and stayed there, living with his uncle and aunt. He co-founded Kommune II in 1967 and joined the Red Army Faction, also known as the Baader-Meinhof Gang, in 1970.
He was arrested with Andreas Baader on 1 July 1972 and was convicted on 28 April 1977 and sentenced to life imprisonment. Like Baader and others, he committed suicide in Stammheim prison in Stuttgart on 18 October 1977.