König was a medical service officer who often observed the experiments of Josef Mengele, reporting to various medical firms and authorities in Nazi Germany. König joined the Allgemeine-SS in the mid to late 1930s, converting over to the Waffen-SS once World War II began. There are no records of König ever having served in combat, and the first significant mention of him in Nazi records occurred in September 1944 when he was assigned to Auschwitz.
Initially, König worked at the main camp hospital at Auschwitz I. Here, he was known for experimenting with electro-shock therapy on male camp inmates. He soon received an internal camp transfer, and was next assigned to the Birkenau camp where he became a medical liaison to Josef Mengele. In her post-war memoirs, Eva Mozes Kor gives specific mention of König, specifying that he was often with Mengele during the latter's experimentation on twins.