The transformations Ansar Shahhoud underwent—what she endured, and the team that helped expose the Tadamon massacre—form the core of Killing Anna, the new documentary by Sam Benstead. Filmed over four years, the film traces the story of a massacre, a war criminal, an academic investigation, and a journalistic pursuit. It also forces us to confront the slow erasure of Ansar herself, and the way Anna—the persona who stared into the eyes of men acc…