 When the Wehrmacht later called for his service, T4 prevented his transfer.Along with other T4 recruits, Frenzel reported to the Columbia Haus in late 1939, where he was first checked for political reliability and then watched a film on the supposed degeneration of handicapped people.He first worked in the laundry and as a guard at Grafeneck Castle, then he worked in construction at Bernburg Euthanasia Centre, and finally became a stoker at Hadamar Euthanasia Centre.