In the Warsaw ghetto, Emanuel Ringelblum and the other members of the documentary group Oyneg Shabbos collected whatever they could to recount life in the ghetto; newspaper articles, erudite texts, even concert tickets and children's drawings. When they learnt of the death at Chelmno of Jews from neighboring towns and from the Lodz ghetto at the end of 1941, they realized that the Nazis and their local auxiliaries had embarked on an operation of annihilation. In mid-March 1942, the ghetto of Lublin was liquidated and the round-ups of Jews continued - with the process of annihilation accelerated after the assassination of Reinhard Heydrich, the head of the Reich's security services and organizer of The Final Solution.