I drew this image where, as in the book, the cat represents a Nazi and the mouse represents a Jew. As this picture is both literal and figurative, you need to take a closer look to completely understand it. The literal aspect of it is that the Jew (mouse) is being killed by the Nazi (cat).
As you can realize with a closer look, the indefensive mouse is being intimidated by the cat since the cat is both larger and stronger that him. I portrayed the mouse standing still instead of running, as he is so afraid and resistless, that he is unable to move. Though the cat is not armed, he is still able to kill the mouse in a split-second, just by stepping on him.
(Real life) To the Nazi's, Jews were nothing, but something that had to be eliminated. Their major concern was getting rid of the Jews, done so by killing them.
In my image, the cat is stepping on the mouse as if it meant nothing. He is killing the Jew as we (humans) kill cockroaches or other insignificant animals; by stepping on them. Most of us do not feel regret in killing cockroaches, the same way the Nazis didn't regret killing the Jews at the time.