Behind me is the scene of an inferno fueled by pure evil marked by voice -- and 911 calls that stunned us all. The first from a father on a murderous Rampage saying goodbye the other from a frantic... See More
Behind me is the scene of an inferno fueled by pure evil marked by voice -- and 911 calls that stunned us all. The first from a father on a murderous Rampage saying goodbye the other from a frantic caseworker screaming for help. Tonight we've got the story you haven't heard yet the last few explosive moments from the only survivor. And what went wrong from the very beginning with Josh and Susan Powell. This story goes all the way back to the sins of Josh Powell's own father. And ends with two innocent little boys who love bugs frogs and matchbox cars. Everything I was supposed to do everything right in the -- is -- yet. Last Sunday's inferno has been sweeping across American television's all week there was only one survivor. She hasn't been heard from until now. It was unreal to me that Josh -- it's -- he murdered his children. -- -- -- -- Elizabeth Griffin hall is the Washington State caseworker who escorted seven year old Charlie -- five year old Braden -- visitation with their dad. Josh Powell I don't psychic damage to the boys. What is the hardest things for you deal with emotionally when you think about losing your voice that they won't go up that they didn't see -- this time and stay. We'll have more of Elizabeth's exclusive inside look at -- still evolving drama that seems in these scenes like hell on earth. But it's a story that begins with a couple who seemed heaven bound. Susan Cox and Joshua Powell. Both mormons and Puyallup Washington natives they met at a church function. Susan's parents remember things moving quickly. How old -- which he decided she'd -- the -- she wanted to marry now going. Nineteen there she was young then young and she just felt like a princess. Susan and Josh were married in April of 2001. The two clans were destined for a strange and explosive relationship. No one saw this coming in the young couple's early bliss certainly not Susan's sister Denise. At the very beginning -- perfect couple very happy couple virtually everyone who met Susan speaks of her warmth and openness qualities that impress their new neighbors when the Powell's moved from Washington to West Valley City, Utah. She was always worrying about. Other people. Where Josh was kind of the exact opposite. -- was only ever concerned about himself. Seeking feet Darlene Allen a friend since childhood says Susan confided everything -- -- What do you know to be the truth of this marriage at Houston. Syrian peace and and he owner who -- -- -- the Bruins who did you think about leaving. -- -- -- check you can't say but friends say Josh used a powerful weapon to keep Susan in the increasingly volatile marriage their sons. Charlie and younger brother -- But I told her leave with the kids she told me that he had told her over my dead body -- you have those sports. There might -- again the voice work possession to hand in his possession. Would fathers and sons is one -- with deep dark -- in this story. It's now just come to -- that Josh himself may have suffered at the hands of his father Stephen. Documents obtained by 20/20 from Steve Powell's 1992 divorce from his wife Erica -- a disturbing picture of Josh. As a severely troubled teenager under the thumb. Of an abusive father. -- and -- wrote that Josh was exposed to pornography by his father at a young age. He once tried to commit suicide. And most shockingly he threatened his mother with a butcher's knives after she asked him to do -- -- If Susan knew about any of this she never mentioned it to Denise we're -- -- Even as Josh -- behavior grew ever more crew. He would withdraw affection for season. So much so that she knew the exact date of conception for -- and because I heard the F perhaps and. In a marriage headed toward meltdown. At another classic marital pressure and financial troubles. In April of 2007 and Josh who worked in real estate and web site designed declared bankruptcy. But he was trying to come out of it he said he was putting his family first. People who know me know that. -- -- I work hard and put my son's 1. December 6 2009. On that fateful Sunday night Josh and his sons disappeared for almost 24 hours Susan Powell disappeared for what may be forever. On Monday morning December 7 when Susan didn't drop the boys off as usual. A concerned baby sitter called Josh -- sister Jennifer graves. We've tried to knock on the door. And it's. When we couldn't get anybody -- -- the place. Jennifer is among the first inside the house that morning. She says -- phone and purse were left behind. I need (%expletive) and walkway with that. And there's something strange about the living room rug never to great big box fans pointed right at the -- heads in the living room. More and get looks like somebody had washed -- hands. Late that Monday Josh turns up with the children mom tells everyone when his wife disappeared he and their sons ages two and four. We're -- campaign and what time did you go camping. I -- You know I I got out to -- late start. Nine -- some from. -- -- -- Heading to the suspicion Josh Powell doesn't get around -- -- Susan's parents chuck and Judy Cox until two days later. Did he offer any. Explanation of where she -- gun. Now they were having trouble nation -- left me -- here. No nothing like them. He is that I I don't know where she rules. No idea where she where would you start looking know I don't know I don't know where to go tonight on night line up without a Trace. In the case of that missing -- the missing Utah mother becomes national news. Everyone wants an answer why take -- two young sons camping. After midnight. Freezing cold temperatures. Well. We just go out and do things that are part. Police named Josh Powell as the only person of interest but they stop short of calling him a suspect. Then he disappears himself. He knows she's not coming back. She's missing and he -- A month after that's ridiculous. Nobody does that. It's only hit me. Justice done something to her. Powell and his -- turn up in his hometown near Seattle living with his father and Josh is through talking to cops -- but not. -- your life. Suggest anything to do with the disappearance of their life. The investigation may be stalled but there are other developments. -- summer camp in 2010. The younger boy Braden and sketches and innocent drawing with the dark complications. And he -- a minivan. At least three people that there's daddy in their. Charlie and there's me. Says all that's nice money -- -- mommy's in the trunk. Now and then he said well you know we went camping and we stop somewhere in -- -- got out -- didn't come back. Still cops say there's not enough to make -- -- rest. Increasingly frustrated police allegedly turn up the heat Josh. Fox family lawyer Steve downing says Simpson's family was encouraged to pass out flyers in a shopping center -- writing in the Powell's neighborhood. And a massive and very public search in a desolate mining area is seen now as a way to provoke the prime suspect. It worked on Joshua didn't make him come around noon acknowledge anything of confessed but it's certainly round tomorrow I think -- -- Valley city police would neither confirm nor deny this account -- the playing mind games the owls had launched a strategy of their own attacking of all people Susan. I don't really think she's dead never and -- -- since that time and really haven't. Felt that way in this stunning interview with -- -- -- Josh -- Wife may have led a -- life back and illicit affair foul play was at the bottom of her abrupt departure. Has she ever been unfaithful to you. Ever going. Then why do you think that she would just run off with -- -- teens and parents sexual from. A Powell and his mother go so far as to implicate this man. Thirty year old Steven Kutcher -- who coincidentally disappeared just days after Susan. Although Kutcher was last seen near Las Vegas 400 miles away from West Valley City was there any chance that was true you're going. No actually went into moment. He made me think ridiculous. This ridiculous Folsom police departments -- since December that's really nothing there.
This transcript has been automatically generated and may not be 100% accurate.