What happens to leper lepellier in A Separate Peace?

When Gene caused Finny to fall from the tree in the beginning, Leper saw what happened. Then when he enlists in the army he is overwhelmed. The burden of what he saw and the stress of the war are too much for him to bear and he goes mad. He later returns to Devon and tells the boys what he saw, leading to Finny's fall down the marble steps.