"You couldn't have done anything to stop it, Katniss." She'd hate him when he tells her. So, of course, it's best to say it while he has her pinned after a fashion in a tight embrace. "I put myself between the blade of an axe and a...comrade on purpose. I knew it would end in my death. And I stepped into it all the same."

To keep his word. Given without saying as much, but made all the same.