Why is it ironic that Hans suffered feelings of guilt after giving the dying Jewish man a piece of bread?

When Hans sees Jews being marched through town on their way to a concentration camp, Hans gives an old Jew a piece of bread and is whipped by a soldier for doing so. After that incident, Hans anticipates the secret police taking him away; when he sees two Nazis wearing black trenchcoats on his street, Hans even runs out and tells them that it's him they want.