Born in Vienna, Grabner joined the Austrian police force in 1930 and became a member of the then-illegal Nazi Party in 1933.

He was transferred to Auschwitz concentration camp less than one year later where he became Chief of the Politische Abteilung ("Political Department").

As Gestapo chief, Grabner was responsible, among other things, for the fight against the resistance movement in the camp, as well as for the prevention of escapes and all contact with the outside world.

These tasks were carried out with horrendous cruelties against the prisoners and a large number of incarcerations in the bunker in Block 11.

Grabner's staff members, such as Wilhelm Boger, who was only brought to justice in the early 1960s, carried out so-called sharpened interrogations, during which the victims were systematically tortured.