images in her exclusive report are disturbing. reporter: the work is delicate. the kind of excavation usually reserved for historic artifacts. now put to grim use, to exhume the first bodies from tikrit s mass graves. a pause for a brief ceremony to honor the dead. reporter: the iraqi national anthem plays. the lyrics of unity float across the freshly open ground. no one yet knows who the victims are, but it doesn t matter. i have been working on exhuming mass graves for eight years, but something like this, it s different because of the way they were killed, this man says. as many as 1,700 shia army recruits were marched to their death by isis when it swept through here in june in what is now known as the speicher