Julien gets tackled while trying to leave the Verrières church. He's arrested for the murder of Madame de Rênal. He basically knows he's finished. Little does he know that his shots haven't killed Madame, but only wounded her.
A judge visits Julien in prison. Julien tells him that he killed Madame out of cold blood and that it was all premeditated. It's like the guy wants the death penalty.
He writes a letter to Mathilde explaining what he's done.
Later, he finds out that Madame de Rênal isn't dead. Then he just starts bawling over what a mess he's made out of his life.
Julien thinks about bribing the guard to help him escape, then forgets it because he doesn't really care enough to bother.