After the Nazi invasion of Austria, Heinz and later his sister Liane were sent to safety in England via the Kindertransports. The parents hoped to join their children in England or elsewhere, but never were able to obtain a visa to safety, and perished in the Holocaust. The Leo Baeck Institute in New York has the letters the parents wrote to Heinz in England from 1938 to 1942. The letters have also been translated into English, though the translations are not yet available online. The original material is digitized and can be accessed by going to the Leo Baeck Institute website and typing in "Ludwig Katscher Collection" in the catalog search field.