How did the Rosens find out that the Nazis had their names on their list?

The rabbi informed his congregation at synagogue that the Nazis had taken all information from the synagogue lists.

"This morning, at the synagogue, the rabbi told his congregation that the Nazis have taken the synagogue lists of all the Jews. Where they live, what their names are. Of course the Rosens were on that list, along with many others."

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