Why does Mr. Weisfeld panic when Claude awakens him at four o'clock in the morning to share his new composition?

Mr. Weisfeld panics when Claude awakens him at four o'clock in the morning to share his new composition because he is reliving the horrors he faced in Nazi Germany during World War II, fears that never leave him. Mr. Weisfeld thinks the Nazis have found his hiding place and are there to arrest him.