Before being transferred in May 1943 to the Majdanek concentration camp, again as adjutant to Weiss, Höcker followed a course at the SS military academy (Junkerschule) in Braunschweig.

Afterward, he became adjutant to Richard Baer, in 1944, who was previously deputy to WVHA chief Oswald Pohl in Berlin.

In May 1944 Höcker was transferred to Auschwitz, where he remained until the advance of the Soviet Red Army forced camp evacuation in January 1945.

He further denied any knowledge of the fate of the approximately 400,000 Hungarian Jews who were murdered at Auschwitz during his term of service at the camp.

On 3 May 1989 a district court in the German city of Bielefeld sentenced Höcker to four years imprisonment for his involvement in gassing murders of prisoners, primarily Polish Jews, in the Majdanek concentration camp in Poland.

Camp records showed that between May 1943 and May 1944 Höcker had acquired at least 3,610 kilograms of Zyklon B poisonous gas for use in Majdanek from the Hamburg firm of Tesch & Stabenow.