He fled to the Netherlands, then to England, where he was appointed to the National Council of the Polish government-in-exile. He interviewed Jan Karski and tried to publicize the mass murder of Jews in German-occupied Poland. After the Warsaw Ghetto Uprising was brutally crushed, and Warsaw's remaining Jews murdered by units under SS-Brigadeführer Jürgen Stroop, Zygielbojm committed suicide to protest the inaction of the western Allies.