In Act 3, Kate tells Joe that he has to fess up to his guilt and even go to jail if that's what Chris wants him to do. Joe can't believe what she says. He's based his whole life on making enough money that his family would have everything they wanted; he's done nothing but make sure they have what they need. Joe defends his actions based on the fact they were performed for the family unit as a whole. Kate explains that Chris sees the situation as something more.
After Joe hears the content of Larry's letter (that he plans to kill himself because he cannot live with his father's guilt), he views things differently and agrees to turn himself in, but that never happens. Joe shoots himself (suicide).