On September 3, the group was deported on what would be the last transport from Westerbork to the Auschwitz concentration camp, and arrived after a three-day journey. In the chaos that marked the unloading of the trains, the men were forcibly separated from the women and children, and Otto Frank was wrenched from his family. Of the 1,019 passengers, 549—including all children younger than fifteen—were sent directly to the gas chambers. Anne had turned fifteen three months earlier and was one of the youngest people to be spared from her transport. She was soon made aware that most people were gassed upon arrival, and never learned that the entire group from the Achterhuis had survived this selection. She reasoned that her father, in his mid-fifties and not particularly robust, had been killed immediately after they were separated.
That same day, Gestapo official SS Sergeant Karl Silberbauer and two Dutch police collaborators arrested the Franks; the Gestapo sent them to Westerbork on August 8. One month later, in September 1944, SS and police authorities placed the Franks, and the four others hiding with the Franks, on a train transport from Westerbork to Auschwitz, a concentration camp complex in German-occupied Poland. Selected for labor due to their youth, Anne and her sister, Margot were transferred to the Bergen-Belsen concentration camp near Celle, in northern Germany in late October 1944.