When World War II began, Kataszek left Warsaw for Lviv, which was under Soviet occupation; when in June 1941 the Soviet-German war erupted, he returned to Warsaw and entered the Warsaw Ghetto. He led the Jewish Ghetto Police Orchestra. When deportations to Treblinka and Bełżec started, he escaped to the "Aryan" side of the wall and went back to Lviv. He went back to bandleading but was recognised by an SS officer, arrested, sent to Pawiak prison in the Warsaw Ghetto, and shot on 22 May 1943.