we know that he has -- >> do we know that? >> well, i -- let's say, i allege that. i believe that, deep down. >> kratz discovered more in avery's past. 18 years before teresa's murder, avery wrote this letter to his estranged wife from prison, saying, i will kill you. and a former fiancee told police he had physically abused her. and kratz said he learned something even more disturbing. this 2006 police report accuses avery of raping a teenage girl a year after he was released from prison. it all together for kratz. he believed avery had developed a deep resentment of women which had started with his wrongful conviction and had only grown over the years. >> he has no remorse for his behavior, feels incredibly entitled. >> but as he continued to investigate the case, kratz had a problem. you still didn't know how she was killed, exactly where she was killed.