At one point, the family lived over a Jewish-owned bookstore. They were captive witnesses when the Gestapo made a late-night raid burning not only the store's contents, but also burned the store's owners alive atop the pile of burning books.
The passage describes a horrific event where the Gestapo raided a Jewish-owned bookstore and set the owners on fire while they were still alive. The family was forced to be present during this act of violence.