Shed opened her home to. What no one could understand was why . Something else had to have been at play here. Reporter indeed, this case was about to get a lot more complicated stories of a diabolical plot, brewing behind closed doors. This is really just betrayal on top of betrayal on top of betrayal, isnt it . Reporter and an obsession that would not be denied. It was like, i want this. This is how im going to get it. Reporter im lester holt and this is dateline. Heres Josh Mankiewicz with deadly betrayal. Reporter there comes a time in most cops careers when they see something so horrific, theyll do just about anything to forget it even though deep down they know they never will. For officer randy mullenex, that moment came in november 2012 on a call to chagrin drive in Willoughby Hills, ohio. You ever have a scene like this before . Never. Ive never seen a crime scene like that and i hope id never have to again. It was bad. Reporter finding out what happened that night on chagrin drive, and why, would ultimately lead investigators on a journey that would reveal accusations of a diabolical murder plot and a series of betrayals that tore apart an american family. That journey would begin when this house of horrors was still the loving home of lisa and Kevin Knoefel, a couple whose friends describe as destined to be together from the moment they met. I remember her talking about him, and she had nothing but great things to say. Reporter lisas close friends, kayleen and karl lessmann, were the unofficial chaperones of lisa and kevins first date. They come in and he is fabulous we got along right away. I mean he fit right in, seriously. I can totally see why she was drawn to him. I mean, you really can. Reporter kevin was just as drawn to lisa, according to kevins sister krisanne sutton. I remember kevin telling me, i met somebody. And her name is lisa. And i think i really like her. She liked to have fun, just like kevin, very family oriented. And good for him . Very good for him. Reporter both kevin and lisa had been married before. And both had children. Lisa had megan. Kevin had cody. Kevin was always good with children. Reporter linda cover is a knoefel family friend who has known kevin all his life. Good father . Good father. Dedicated father . Absolutely, absolutely. Reporter kevin was a jack of many trades a truck driver, a school bus driver, an emergency medical technician. Lisa dedicated her life to social work, helping and caring for sexually abused kids. Kayleen was one of lisas coworkers. She just wanted to help people. We work in a sex abuse unit and thats a very difficult subject that a lot of people cant deal with, but she really prided herself on helping these families and being able to help, you know, make a difference. Reporter everyone admired lisas selflessness. Her friend carrie ward also worked with lisa. She took in foster kids while she was a single parent and was raising her own daughter by herself. That feels sort of like going the extra mile and then some. She did. She was always there to help anybody that needed it. Admirable. Yes, very much so. Reporter one year after kevin and lisa met, they married. The wedding itself, i mean, was fabulous. The reception was great. Did you think this marriage was going to be it for kevin . Oh, absolutely, absolutely. There was no question in my mind. Reporter a year and a half later, lisa and kevin announced the arrival of a baby of their own hailey. Lisa was on top of the world. Megan she loved like crazy, of course. But she really wanted another child. Reporter but lisa felt she had more to give. Two years after haileys birth, she decided to invite 16yearold foster child, Sabrina Zunich, into her home, and to make sabrina part of the family. I met sabrina almost immediately when she came to the house. And i remember her saying, i finally have a family. Everything was going really well. She fit right into the family. Lisa, i mean, couldnt talk highly enough about her. Reporter but the happy times for the knoefels blended and now extended family would come to a catastrophic end on that november night back in 2012 when lisa knoefel was brutally stabbed in her home. When i heard it was lisa and who did it, i couldnt believe it. Its like, youre kidding me. A devoted mom, attacked in her own home, enough to shock any family. But the story behind this crime would leave the knoefels nothing less than shattered. The blade was actually bengt. T. I just started shaking my head because it takes a lot to bend a knife blade. Who could have felt enough rage to do that, and why . To find out how you and your doctor can take the next step towards a cure. Because the answers you need may be closer than they appear. How can you see yourself in new glasses. Without your glasses . 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Oh, my god, my moms going to die reporter in the background, lisa can be heard, pleading for help. Call 911 what is going on . Oh, my god its really chilling to listen to. Youre going to have to take a deep breath. I cannot understand you. My moms going to die reporter first responding officer randy mullenex arrived at the knoefel home and found megan frantic at the front door. Shes waving her hands. You need to hurry. Hurry, hurry. Reporter mullenex learned Kevin Knoefel was away on business leaving lisa, megan, hailey and their foster daughter sabrina at home. Worst Case Scenario was going through my head. What am i going to see . How bad is this going to be . Reporter it was far worse than he could have imagined. Out of the master bedroom came the knoefels 18yearold foster daughter, sabrina, holding a knife. It looked like she she literally showered in blood. Reporter mullenex ordered sabrina to the ground where she was cuffed. He then went to the bedroom where he found lisa knoefel on the floor. I could barely even see flesh color. There was that much blood on her. I knew there was nothing i could do. Reporter the coroner would later determine lisa had been stabbed and cut more than 178 times. Sabrinas weapon was a 15 inch bread knife. The blade was actually bent. And i just started shaking my head cause i couldnt it takes a lot to bend a knife blade. Reporter with Sabrina Zunich now booked and in the lockup, detective Ron Parmertor began the investigation. This wasnt a case in which you had to wonder who was responsible . Thats correct. We knew right away it was the foster daughter. Reporter this looked like a case that could be shut as quickly as it opened. But if that were true, we wouldnt be telling you this story. This turned out to be one of the most unusual cases weve ever come across. Police would end up investigating not just who but why with answers as stunning as they were disturbing. As dawn broke that cold november morning, detective parmertor began with his perpetrator, Sabrina Zunich. I first noticed that she was a very small girl, very frail girl. Reporter sabrina started describing the moments leading up to the murder. Shed had a migraine, she said. While everyone else slept, she walked into the knoefels master bath to get some ibuprofen. And that, she said, is where her memory went blank. You didnt think anybody could stab somebody that many times and not remember any part of it. No. I tried all different ways of, you know, get her to come out and tell me what really happened. And she was not giving it up. Reporter and then sabrina asked for an attorney, bringing parmertors interrogation to an abrupt and frustrating halt. You thought, whatever else were going to get, its not going to come from her. Exactly. Reporter so, parmertor consulted those who arguably knew this teenage ward of the state better than anyone sabrinas social workers. She had some issues growing up. Her grandma took custody of her about the age of three. Reporter case manager Nicole Corbett said sabrina struggled with having been abandoned by her parents at a very early age. She ended up in the juvenile system after stealing from her grandmother to pay for drugs and alcohol. She worked a lot, in counseling, how to cope and how to manage with everything she was going through. Reporter eventually, nicole helped place sabrina in the knoefel home. She just wanted to be a part of something, a part of a family. I know thats what she wanted more than anything. So, when she was told about being placed with the knoefels, she was ecstatic. Reporter it turned out the knoefels loving care was just what sabrina needed. She was going to class, getting good grades. I think sabrina really was thriving in their home. Reporter which made the news that it was sabrina who had brutally stabbed lisa all the more baffling. I still cant see the sabrina that i know being violent towards anyone, let alone what she did. Something else had to have been at play here. Reporter detective Ron Parmertor was thinking the same way. He wanted to talk to kevin about what that Something Else might be but he held off. I was giving him his space because i thought that he needed time to, you know, deal with the tragic death of his wife. Reporter according to sister krisanne, kevin was an emotional wreck when he heard what happened. Im sure that there was some guilt because he worked nights and he wasnt home. Hes like, i never thought this would happen. Did you think he had anything to do with this . No. You could definitively prove that kevin wasnt even in the house at the time . Absolutely. Kevin was on the ohio michigan border at the time. Reporter still, he felt kevin might hold the key to solving the riddle of this case. Why keep going . You got your suspect and shes got the weapon in her hand. I was just doing my job as a detective. I was trying to find out why. Reporter it was the one central question that continued to plague detective parmertor and drive him forward. Youre crossing your fingers and thinking we really need a break. Yes. And then one day it arrives. One day, sabrina decides that she wants to tell us what happened. Reporter and the story sabrina ultimately told was far more complicated and twisted than anyone could have imagined. Coming up, investigators hear stories about tensions in the knoefels seemingly happy home, triggered by sabrinas odd behavior. It made lisa uncomfortable. Lisa wasnt happy with it, no. Sabrina says she wasnt the cause of problems in the house, but the victim. It really it hurt me. When dateline continues. Dreams are born. Hopes fly high. We love this country with a passion. You can see the pride in our eyes. Read the joy on our faces. Hear the love on our lips. We create products that deliver an effortless beauty look. 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Reporter news of lisa knoefels bloody murder cut through Willoughby Hills, ohio, like a blistering winter wind. I was shocked. Lisa was a nice person. She was a good mom. She was a good wife. For someone of that much beauty and that much giving of herself to just be taken from us like that, its just too much. Reporter finding out that the foster daughter lisa welcomed into her home ended up committing lisas murder added to the collective pain and suffering. Betrayal is the perfect word for what happened. Somebody hurting her that she had taken in. I just cant even imagine what she must have been going through. Reporter as detective Ron Parmertor worked the case, he learned thered been growing tension within the knoefel home right before the murder, and the source of that tension was sabrina. She got along great with kevin, and she did not get along well at all with lisa. Reporter parmertor discovered lisa had become frustrated with sabrinas behavior toward kevin. She was fascinated with kevin. She seemed a little vivacious in my eyes. Flirty, like flaunting herself. Reporter and parmertor learned from texts on lisas cell phone that sabrinas flirty behavior had begun to take its toll on lisa and kevins marriage. Sabrina was demanding kevins time, and kevin was making himself available, too available, as far as lisa was concerned. You have one actual text from lisa to kevin in which shes saying, youre getting too close to sabrina . Yes. Reporter in fact, lisa wrote, cut the damn cord. Spending too much time with her and less with your real family. Thanks a lot. Lisa also became concerned about the relationship sabrina had with her daughter, hailey. She acted like a mother to hailey on a regular basis. Reporter it made lisa uncomfortable . Lisa wasnt happy with it, no. Reporter it sounds like one of the things everyone agrees on is sabrina was fixated on, fascinated with hailey. She was. I think she was infatuated with the whole family and she wanted to be biologically in that family. Reporter parmertor learned that just weeks before the murder, tension between lisa and sabrina had reached the breaking point. After 17 months under the knoefel roof, sabrina was told it was time to pack up and get out. Sabrina got very upset and knew that lisa was the one initiating that action. And what, snapped . Yes. Reporter but right now, all that was just a theory. Then, six months after the murder, the investigation took another turn. Parmertor learned sabrina was ready to talk. She starts telling her story. She starts sobbing. Tears are coming down her face. Reporter sabrina told dateline the same story she told police. It was a story of a young girl bouncing through the foster care system, always dreaming of a better life. I wanted a new beginning, and to put the past behind me. I wanted that picket white fence, the dinner around the table with siblings, you know, something i never had. I wanted that structure of a family. Reporter so when the knoefels opened their door to sabrina, it was a dream come true. My First Impression of kevin was a caring father. Somebody that was willing, you know, to get to know me and want to know me. Reporter and then there was lisa. My relationship with lisa, it was, at first, good. We would all spend time together. We would go swimming in the backyard. I felt a part of the family. Reporter then sabrina confirmed what parmertor had already heard. The good times quickly came to an end when sabrina and lisa started arguing. According to sabrina, lisa began thinking of her as more foster than daughter, and sabrina didnt like that. I felt like the outsider. I felt kind of abandoned, in a certain type of way, and not accepted. Reporter sabrina admitted her close relationship with both kevin and hailey had become a major source of friction with lisa. She doesnt like the fact of how im acting with hailey and wouldnt let hailey come around me, not even give me a hug at night. It really, it hurt me. Reporter and then came that moment when sabrina said lisa told her it was time to go. She was very blunt about it. And she was like, im sorry but i dont want you here anymore. My life was shattering before me. The betrayal, the abandonment, all that came to the surface. Reporter two weeks later, sabrina says she quietly, carefully walked into lisas darkened bedroom, a knife in her hand. I was in the room for a good 10, 15 minutes. It was a constant battle in my head. It was, like, just do it. Dont do it. Just do it. Reporter in the end, it was sabrinas darker side that won out. She wakes up and she thought i was megan and was like, megan, go to bed. I completely froze and then she sits up in her bed and she was like, megan, go. And she realized it wasnt megan and thats when i did it. I remember her shouting, brie, stop. I remember megan coming in and setting a hand on my shoulder and saying brie, stop. And i just nudged her off and told her, megan, dont. Reporter anger, triggered by a troubled teenagers feeling of abandonment, leading to murder. For Ron Parmertor, sabrinas story made perfect, if tragic sense. You believe sabrina . Absolutely. Reporter but sabrina was not done. What she was about to reveal would send this investigation hurtling in a completely new and alarming direction. Sabrina told detective parmertor she didnt act alone. I couldnt have d