Why did Frau Holtzapfel stay in her house during the raid? Why did her son go to the shelter?

Frau Holtzapfel stayed in her home because she was ready to die. Michael stayed because he wanted to live.

“Tell me something,” he said, “because I don’t understand. . . .” He fell back and sat against the wall. “Tell me, Rosa, how she can sit there ready to die while I still want to live.” The blood thickened. “Why do I want to live? I shouldn’t want to, but I do.”