. >> we talk with tom fassbender, a lead investigator under fire for this controversial interrogation. >> you've stayed silent through the firestorm. why are you sitting here today? >> finally realize that someone needed to speak out to bring forward the truth of what happened. >> reporter: so what did happen here? our story begins with the woman at heart of this case. a 25-year-old photographer from kaukauna, wisconsin, named theresa halbach. >> she loved being behind the camera. >> reporter: kim peter sson and she became friends in college. kim said theresa had a special way with her suspects. >> she loved to make other people smile. >> reporter: the two stayed in touch an graduation as they launched their careers, but that would all change suddenly in too 2005. >> the 25-year-old photographer on assignment for "auto trader" magazine when she disappeared. >> my heart dropped knowing it was somebody i knew. >> reporter: quickly a massive search was launched. after two days a big break. >> we have found -- >> reporter: they found her vehicle. >> reporter: tom fassbender then a special