There are many points in the novel Night in which Elie is ashamed of his behaviors. It all stems from the theme of survival and the animalistic instincts that come out in men when they are 1.) trying to survive and 2.) being treated like animals for so long.
Being treated like animals starts right in section two when they are carted to Auschwitz on cattle train cars. They are huddled together in masses, terrified of what is coming next and because of the women who keeps yelling that she sees fire. The first shameful incident is when the woman on the train is gagged and beaten into submission. Elie can't but help feel relieved that she is no longer able to scream and terrify the others.
The most intense feelings of shame and guilt occur toward the end of the novel when Elie's father is close to death. He has dysentery, and he refuses food and water except for when Elie forces him to take it. Elie resents his father and even contemplates stealing his father's ration of food and water for himself. He resists the temptations.
Elie fakes sick to stay with him during the days because other men beat him and steal his food and water during the day when Elie was gone. One night, Elie's father calls to him from his bunk, but Elie is tired and sick of taking care of such a burden. He ignores his father, and is horrified to find his father's bunk empty when he wakes up.
Elie never knows whether his father was even dead when the guards took him in the night and threw him in the crematory. But Elie doesn't feel sorrow or fear at first, instead he just thinks "I am free at last." This immediate thought makes Elie feel truly guilty for not being there when his father was dying to protect him and hold his hand as he passed.