Langen was arrested by the Gestapo on 17 December 1943 and brought to the Gestapo prison of Cologne for interrogation. After a few days he was moved to the Cologne prison "Klingelpütz", a wing of which was used for Gestapo prisoners. As the "Klingelpütz" was damaged in the Allied bombing of Cologne in 1944, he was later moved to the Siegburg penitentiary. He died there from epidemic typhus on 16 March 1945.