Im putting alarms on every door because somebodys out there. Detectives, they decided the killer wasnt out there but inside the house. Now, with one of their own under arrest, the family was furious. You see these people . This is love. This is is belief. This is human beings. Please listen to us. Did investigators rush to judgment . Do you have any idea beyond your own fevered imagination what thats what happened . You dont have a clue. I think that i do have a clue. Was the real killer still out there . Im lester holt, and this is dateline. Tonight, Keith Morrison with the a killing in cottonwood. Narrator on the afternoon of may 4, 2012 casey deayas walked out for his favorite thing high school baseball. A doubleheader. Spring of in its full glory in northern california. His senior year of almost done. This was of the place he loved. The game he loved. People sometimes talk about having premonitions of things. Did you have anything like that at the all . It was another day. Another one of my countless baseball games. Countless baseball games. Reporter narrator wasnt of course. No no one though no one knew it as they sat the there that afternoon. Reading, california with its sun dial bridges, Middle America feel srg a feel, is a different feel, different life of from the botoxed and tmzd events of the south. Drive a you few miles and youre on the the ball diamond of cottonwood in the shadow of mighty mt. Shaft ofa. An anchor shasta. An anchor a constant just like people who knew casey would be in the stand. Were they there . Both there. Reporter always there . Always there. Never missed a game. Reporter his parents, mark and karen, dwanus. Side by side by the dugout as always. They were together since they were what 17 years old. Practically lived in each others skin . Exactly. His mother had brought the chocolate chip cookies she passed out to the players after every game. And for which she was of justly famous. His father had made sure he finished work in time for the opening pitch. What kind of parents were they . They were the best parents that you could ask for. Reporter this is jason could their eldest son. And here the photo of jasons graduation with his proud parents the day he became a fireman. They would do anything for us, and they did. Reporter mark and karen were from big mormon families High School Sweethearts, who married as teenagers and watched their own brood quickly expand all boys jason jacob, tyler, troy and casey. Boys bursting with testosterone. It was of a rowdy house. We had Football Games inside the house. We were egged on by our parents, and they loved it. Reporter karen of a fulltime mom and once the boys were old enough taught part time at shasta college. For decades, mark got up at 2 00 a. M. To drive for u. P. S. Just because it freed him to coach his sons teams come afternoon and to spare his wife middle of the night disruption. Mark slept in a separate bedroom. Had for years. My dad treated her better than anybody could treat their wife. My mom of the queen. They lived simply. They lived paycheck to paycheck. They never had a lot extra. Reporter son tyler. For them it was all about family . Always. Reporter they stayed as close as any family could be. When jason got married, he moved into the house right next door helped celebrate mark and karens Silver Wedding anniversary as they all did. By 2012 they were grandparents many times over had been married nearly 33 years. One thing i always looked up to and loved about their relationship was that they still dated. Reporter tylers wife tina. After that long sometimes you can lose that and i never saw them lose that. Reporter the change does come for everyone. And by 2012 in their early 50s, mark and chairmen mark and karen were making changes. Karen went about School Nursing school. This of the plan they talked about . It was the perfect situation. She got to stay home with the kids all growing up and now she was of ready to start her her career. He was stay home, collect a pentagon, and she collect a pension, and she would start nursing. Reporter . So easy of course. Nursing school is a you toughtough thing. Her brother joe and his wife jackie. The commitments changed. Having grandma there when you need her having mom there when you need her. She was of going to have to study. She felt she should be doing better. I remember a tech that said i got back from the empare. R. Got the chance to work with final finally. I love of it. She was on her way. Reporter that may 4th casey joined his parents at home after his ball game. It being friday he and a friend went to see a movie, the avengers. Started at 9 15. And told my parent evers everything was fine. Reporter do you remember the last thing you said to your mom . Shea handed me a 20 dollar bill. I thanked her and left. Reporter it was almost midnight casey immediately fell asleep. What do you remember next . Put my head on the pillow, and two second later, doors open dads at the door freaking out. Reporter and the seconds later 911. Your emergency . Reporter the family of about to discover that a perfectly ordinary even human being ended d evening had ended in tragedy. Blood everywhere. Everywhere. Reporter when we return, a dad deaf stayed. Is one tragedy about to become two . I remember him coming in the door and collapsing falling on the floor. Thats why you need lysol. Because when you use bleach, some stains are left behind. As this dye reveals. Lysol toilet bowl cleaner does more. It removes the tough stains that bleach doesnt and it also disinfects. So why just bleach . With lysol you can do more. Thats healthing. And get max cleaning and freshness with every flush. Try lysol no mess max. Colourists know roots take colour one way, and previously coloured hair another. New Vidal Sassoon salonist. First, brush roots then, blend through lengths. 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But the house of dark everybody asleeping or so it looked to an exhausted casey who fell into bed and almost would inimmediately into a deep sleep. And then 25 minutes later dad takes place doors at the door freaking out, go next door go get jason, somethings happened to your mom. Get jason. Reporter he did as he was told running to his brothers house. 911. Emergency. Reporter his father, mark called for an ambulance. Tell me what happened. She i came in the room, i heard her. And shes got blood everywhere. Everywhere. I dont know i have no idea. You have no idea what happened . No. Oup whereyou dont know where shes bleeding from . No. Just blood everywhere. Are you with her now . Yes. Oh, its in her chest. Theres a gash thisin her chest. Reporter jason woke up to the horror two ways at once. Fire department alarm. Brother alarm. I wasasleep. As a volunteer firefighter i have a pager. I could hear the pager going off. Casey was ofsial yelling in a panic, theres something wrong with mom. You youve got the to. Reporter did you have any idea of what it was . I had no idea. Reporter it was a nightmare beyond dreaming. There was of his father in fullblown panic, and on the floor in a puddle of blood was his mother. The rookie firefighter for an instant to his eternal regret froze. If i would have come on that situation now, i would have immediately started cpr. There was a great deal of blood. So for somebody to live through that that much blood didnt think it was going to happen. I believe i you just missed her last couple of breaths. Reporter minutes later, emts arrived, and karen duenas was pronounced dead. The cause multiple stab wounds including a massive gash to her chest. Long after, the young detective arrived, logan stonehouse. A year under his belt as an investigator. But this would be his first big homicide case as lead detective. And lo and behold i didnt know what i was of talking into until i you saw a picture on the wall and realized whose house i was in. Reporter you knew these people . I did. I went to high school with the second oldest son, jacob. Reporter here he found himself looking at the bloody body of jacobs mother, karen. The lady everybody loved who brought cookies to all the games at school. Who could have done this . Detective stonehouse had been on the force long enough to be aware that Violent Crime of up here. Some said significantly. Ever since californias overcrowded prisons nearby were forced to reduce populations and to had reduce potentially dangerous offender likes like drug addicts, possibly desperate for money like a fix. So was this a Home Invasion robbery gone wrong . The detective took a look around the house. He and fellow officers fanned out around the neighborhood. There were footprints outside the property right . There was. There was a wood fence that surround that piece of the propertiment and property. And theres a back gate and trail that led to a canal area. Reporter the first patrolman told them he had seen a car speeding away as he raced toward the duenas house. Neighbors reported seeing two stranger nearby that evening. And here in this crime scene voep taken the next day, a screen on the window in karens bedroom that looked suspiciously like it had been cut open. Had intrudersen er it entered here . Was anything disturbed . No. The bedroom was intact. There wasnt drawers open like someone had burglarized the place. Reporter it didnt look like burglars had gone that way. Detectives had questions for the only man known to have been in the house all evening the husband, of course mark duenas. What was his story of what happened . He told us that he had been up with karen. They were watching a movie. And then once karen went to bed he tried to stay up longer to watch a giants game. He was falling asleep during it and decided to go to sleep himself. Reporter mark, in his room, karen already down the hall, he said in hers. The detective took mark to the Major Crimes Unit where mark whod been awake more than 24 hours by now, finished the story himself. I arkssleep, i hear crazy noise. You know you hear a cat sound like it wasnt cats. It was a weird scream talking . No. I just heard some weird screaming type stuff. What did you do . I ran i got up because i didnt want those whatever of going on to wake up my wife. Im sensitive like that. And i went to the door by the kitchen, opened it up and looked out there. I didnt see any cats. Shut it. Walked down the hallway, looked under, the lice were onghts were on. I figured shes up. Thats when i found her. Reporter the doctors questioned him, had his change so they could keep his shorts and tshirt for testing and sent him home. I remember him coming in the door and collapsing. Falling on the floor. We were really worried about him because he kept saying his heart so we thought maybe he was having a heart attack. He was he was ofa mess. Reporter as the family planned a funeral, their big sentenced family including karens brother joe and wife jackie descended on cottonwood. Ive never seen a person more broken. Reporter what was your perception of how he took it . Hes take ten incredibly hard. Still does. Reporter along with grief came anxiety. I lived next door. Im worried for my family. Im putting alarms on every door because somebodys out there. Reporter but the police did not seem to think that. In fact, within a day or two, one of the doctors announced no need to worry about some unknown killer stalking the town. Now why would he say that . Coming up, investigators were about to hear a strange tale from none other than karens husband. Sca reporter they measured time in units of pain in little cottonwood, california will during the surreal minutes and hours and days after karen duenas was murdered. The best way i can explain my mom is she was of pure of heart is the best way to do to say it. Reporter the whole big family karens family as well as marks, parents, brothers sisters, gathered to support each other and mourn and struggle with the question that hung in the air who did this. But the word on the street was there was of no there was no question at all. We immediately heard outlandish rumors. Youre going, i dont know where theyre getting this. Reporter the boys heard them, too. Rumors the detectives knew the killer was mark to which the family said ridiculous. I know theres no way possible he could have done it. My parents were best friends from as long as i could remember. Reporter but it that was true then why would detectives be so suspicious of a man married to his High School Sweetheart for almost 33 years . A man without so much as a track ticket on his record let alone a violent act . Its true that when wives are murdered husbands are frequently implicated, and mark did discover the body. But there was another reason. Just minutes after mark sat down to talk to those detectives he volunteered information that sounded to them like a motive for murder. What was of going on in our life, and it scares me when i think about it reporter it was an odd little story. One day at work toward the end of 2010, said morkark, a u. P. S. Coworker asked if he had ever gone on facebook. No said mark he happen. Well asked the colleague, havent you ever wondered what happened to people you used to know . Facebook might tell you. Mark thought about it and said well there was this girl he used to talk to back in high school wasnt a real girlfriend or anything. But he was curious about whatever happened to her. Sure enough the colleague found the woman on facebook. And pretty soon she and mark were texting and talking on the phone, catching up. We talked visited. Kind of got carried away with a little texting here and there. Reporter carried away . Well, that may be a little strong in this age of sexting and lurid electronic damn an dalliances. They did talk and text for several months, even said i love you a time or two. But was it some kind of affair . Well judge for yourself. Was of there ever any pictures sent or anything like that or of it just theres pictures of just maybe me or her, you know little innocent were not into any of that nasty porn. None of that. Just what do you look like now. She had accept a picture of her, its your turn. She does quilts she took a picture of her quilt. Showed a picture to me. Stuff innocent stuff. She had a public of her and her a picture of her and her grandkid. Stuff like that. Reporter and not once did they try to see each other. In fact when an opportunity came up they decided no it wouldnt be fair to their respective you spouses of more than three decade our their kids or grandkids, so they didnt. But as mark told the detectives, karen out what hed been doing when she went through a phone bill and had hurt her feelings. He promised to stop. Except he didnt. Mark bought a secret phone to continue that communication that karen wasnt aware of. Reporter it was the woman who put a stop to it. She said karen this letter postmarked just a little less than three months before the murder asking for forgiveness, promising it would never happen again. Karen told a couple her kids about it all. She was pretty upset for a while. How important was of that . I would definitely say everything together showed that karen of not happy in their relationship. Reporter mark told them otherwise, that it was a happy marriage the texting thing just a blip. But the detectives didnt believe it so they confronted mark. When did you find out that karen was going to leave you, mark . Leave me . Uhhuh. She was never going to leave me. Never going to leave me. Honestly. Reporter in fact investigators believe it backed up what they suspected from that very first night. Here, just hours after the murder weather they firsthen they first ayoucused mark of killing her. I didnt do it. Its crazy. Just like o. J. We need to be out finding the real killer right . Lapd they didnt have to go find the real killers. I know youre doing your job, but i would never lay a hand on i did not hurt her. I did not kill her. I walked in and found her in her condition. Reporter marks family by the way, said he told them all about that texting relationship. They said didnt seem like such a big deal. It sounds to me that it was you just them confiding in each other about their marriages and their families and just an outlet. Reporter her young ever son for youngest son, casey, it explained why there had been tension for his parents a few monthses before the murder. There was a good swap where they didnt get along, but it was a while before. Reporter they seemed to be back together again . They seemed better than ever. Reporter and those claims by investigators about a pending divorce . Not a chance said the boys. They never were going to give up. They taught us that. Im sure a little bit of trust was lost. Up, someone keeps something from you. You but it was something they worked on and they got over. Reporter all that grief infected summer, a cloud darkened over the duenas family. When casey graduated from high school in june i remember walking to where wed be seated and just seeing you know its my dad along with other family members. You know of course it was reporter five months went by that way, as if the early police suspicions had faded away. Of course, we know better, dont we . Coming up mark duenas is in for a bitter shock. He was upset. Like, are you kidding me . What his family did next would surprise everyone. Sort of thing hardly ever happens. Yeah. Like