What did the Nazis do when trains full of Jews arrived at Auschwitz Nazi death camp?

When trains full of Jews arrived at Auschwitz, the Nazis conducted selections where they separated individuals deemed fit for labor from those considered unfit, including children, the elderly, and the sick. Those marked for immediate extermination were sent directly to gas chambers under the guise of shower facilities, while others were forced into hard labor under brutal conditions. The systematic process aimed at the efficient mass murder of the arrivals, contributing to the Holocaust's horrific death toll.