Hößler was born in 1906 in Oberdorf a village in the municipialty of Martinszell im Allgäu, in the Schwabenland of the German Empire.

[6][7] In June 1940, Hößler was transferred to the newly opened Auschwitz I concentration camp as it received the first mass transports.

[2] On 28 July 1941, Hößler accompanied a shipment of 575 selected Auschwitz I inmates to the euthanasia center at Sonnenstein Castle, where they were murdered as part of the Action 14f13 program.

[8] In June 1942, Hößler, together with Otto Moll and Hans Aumeier, participated in killing 168 survivors of a failed uprising in the punishment section of Auschwitz I.

[11] He was then promoted to the senior role of Schutzhaftlagerführer at the Auschwitz-Birkenau women's camp in August 1943, which he directed together with Oberaufseherin Maria Mandl.

Filip Müller, one of the very few Sonderkommando members who survived Auschwitz, paraphrased Hößler's speech given to trick a group of Greek Jews in the undressing room at the portals of the gas chambers: On behalf of the camp administration I bid you welcome.

Oh yes, before I forget, after your bath, please have ready your certificates, diplomas, school reports and any other documents so that we can employ everybody according to his or her training and ability.

[6] In January 1945, as the Red Army overran German positions on the Eastern Front, the SS personnel at Auschwitz evacuated to the Mittelbau-Dora concentration camp.

Auschwitz commander Richard Baer took over the Dora portion of the complex and Hößler was again made a Protective Custody Camp Leader.

[13] On 5 April 1945, as American 3rd Armored Division closed in on Mittelbau-Dora, Hößler led a forced evacuation of prisoners to the railhead for transfer to the still-functioning Bergen-Belsen concentration camp.

On 15 April 1945, Hößler was found hiding among the prisoners in camouflaged clothing and was detained with the remaining SS staff by a unit of the British Army.

The SS detainees were then forced to bury thousands of corpses lying around on the camp grounds in mass graves.