What does Paul tell Kemmerich's mother about her son's death?

Paul tells Kemmerich's mother that he was with him when he died. He tells her that her son died instantly, shot through the heart. He lies and knows that no matter what.... he will never tell her the truth.

I tell her he was shot through the heart and died instantaneously. She looks at me, she doubts me: "You lie. I know better. I have felt how terribly he died. I have heard his voice at night, I have felt his anguish--tell the truth, I want to know it, I must know it."
"No," I say, "I was beside him. He died at once."
She pleads with me gently: "Tell me. You must tell me. I know you want to comfort me, but don't you see, you torment me far more than if you told me the truth? I cannot bear the uncertainty. Tell me how it was and even though it will be terrible, it will be far better than what I have to think if you don't."
I will never tell her, she can make mincemeat out of me first.