A husband, falling apart. He was panicking. He was shaking, crying. Narrator accidents in the wilderness happen, tragically, every day. So why did investigators suspect that leslies death wasnt an accident at all . The evidence at the scene makes us believe that something entirely different happened. He told me she fell 20 feet. Where were the injuries . Why did i not see what i expected to see . Narrator for investigators, disturbing clues in the woods and water. If your theory is right, that is like she was being hunted. Yeah, its almost like a hare and a wolf. Narrator two harrowing accounts of what happened to leslie one seemingly unsolvable mystery. Either you believe crazy story a or you believe crazy story b. Both stories are crazy. Which one do you want to go with . Narrator im lester holt, and this is dateline. Heres Andrea Canning with the secrets of Cottonwood Creek. Reporter winding down a mountain in southwest colorado, waterfalls spill over granite and sunlight filters through aspens and evergreens. Cottonwood creek an onlyinthewest sort of backdrop. These snapshots barely capture it, but who can resist trying . What a spot to preserve a memory. Careful though. This is wilderness the dangerous kind. Shes in the river. She fell and they cant find her. He thinks shes dead. Reporter the frigid currents here can take a life, and also, maybe, sweep away secrets. It was the Perfect Place to commit a murder where nobody would see you. If you go into it looking for trouble, youre going to find it. Reporter and up in those mountains, sometimes questions are left behind. I dont have an explanation for this. But certainly it does truly haunt me. Reporter the story begins with those pictures together. They form a couple husband and wife leslie and fred mueller, married for almost 27 years. They were always super affectionate. They acted like they were two High School Kids that had just started dating. Theyre just all over each other. And youre like, ewww. [ laughter ] reporter these are the muellers three children amanda, the eldest, then ariel, and alex, the youngest and only boy. They were brought up in texas, near the town of san angelo, but for fun the family headed out to their second home in lake city, colorado. Those photos of their parents were taken nearby. They both loved the cabin, and going up to colorado. It was so uhhuh. Pretty. It was in a valley, and there were just and it would like a postcard, the mountains. Yeah, there was a river running right near there. Reporter their rockies getaway was a family place to relax and escape their busy lives back home. What was life like up at the cabin . We would usually go in the summers. Uhhuh. Go hiking together, horseback riding and just kind of hang out as a family. Reporter did you feel like there was a lot of family bonding . Yes. Reporter going on at the cabin . Yeah, definitely. Wed end up having a lot of fun with board games or going out hiking and doing all these different activities together. Reporter in texas, leslie had an ob gyn practice and worked long hours delivering babies. And she was the areas first ob gyn, female ob gyn . She was. She was very much a pioneer in that sense. Yeah. Like, i think the more people told her, you cant do this, she wanted to do it. Uhhuh. Yeah, she was very strongwilled and definitely a feminist in a way, that she was all about uhhuh. Like, i can do anything that any man can do and i can do it better. Reporter in 2004, leslie decided to make a change in her life. She retired from medicine and devoted time to her church. She even studied theology. But, most of all, leslie loved the outdoors, especially riding horses. I think if she had her choice, she would be riding horses every day and then practicing theology. And im sure she wished the days were longer. Reporter yeah, shes like a superwoman. Their mom embraced adventure, and she wanted her kids to as well. One time mom and i went, just the two of us. I hadnt been horseback riding in a while. And so i told her i didnt want to go more than maybe five, six miles. And she goes, okay, well, i found this trail. Its eight miles, but you can do it. And by the time it ended, it was 16 miles. Reporter so she tricked you. Yeah, but we had such a wonderful time. But the next day i was not moving. Reporter as for fred, he owned a multimilliondollar company importing steel for construction. Still, their dad wasnt all business all the time. In the traditional motherly roles, he would definitely step up and wasnt afraid to be mr. Mom. Reporter the mueller kids say their parents fit one another perfectly. Hed make a point of every night to try to do something nice for her. He was so proud of her, too. Theyd talk uhhuh. All the time. Anytime that there was any type of disagreement about, you know, who the dishes werent done or some honey, do chore kind of a thing, they would talk about it until they were completely resolved. And then at the next second theyd be all over each other again and be perfectly happy. Reporter it was a happy weekend at the muellers colorado cabin. May 3, 2008. Now that leslie was no longer working, she was spending much more time up here. That saturday, the spring day was sunny, the highaltitude air still chilled. Morning began with chores. I think we were unloading some hay, doing stuff kind of like that around the house. Reporter so was this just a very typical weekend in colorado . Yeah. Reporter it was just alex, then 14, up with his parents on this trip. That afternoon, the three went to mass in town. Later, after a snack, his parents suggested they cap off the day with a hike to photograph some stunning waterfalls nearby. I was pretty wiped out by that time, and i just kind of wanted to hang out in the cabin and just read a book or Something Like that. So i turned them down on going for the hike. Reporter fred and leslie headed off with her dog gracie, a Border Collie pup. I think she was only 6 months old. Reporter she rambunctious . She she was rambunctious, for sure. Shes the type of dog that when the ceiling fan would be going, she would try to jump up, and like, follow it around. Reporter fred and leslie parked at the base of the trail. Snow still covered the ground in patches. They hiked up, past a small series of waterfalls. Up until they found the perfect spot for pictures. They had arrived at Cottonwood Creek. Fred struck a pose first. Next, leslies turn. One more of fred big smile. And then leslie again. This time with her beloved gracie. Then something went wrong. Its like its just happening in slow motion in front of me. Reporter in an instant, leslie was gone. At the waterfall, shes in the river. Reporter what happened at Cottonwood Creek . Alex mueller was alone at his familys vacation cabin in colorado. I hear yelling and it is coming from down stream. Theres a bonus in store at the petsmart big brands bonus sale. And save up to 20 on all crates, plastic carriers gates from top paw®, kong® and petmate. At petsmart®. [ female announcer ] is your morning trying to tell you something . Maybe we should have gotten him one . [ female announcer ] sweet, chilled, creamy mccafe iced coffee from mcdonalds. Wait thats the teleprompter guy. [ female announcer ] another reason to love mccafe. So im trying best foods with olive oil. Lets see what happens. Thats not best foods on your sandwiches. Its best foods with olive oil. Whaddaya want, a parade . [ laughter ] bring em over here. Come on. [ laughter ] honestly, the offseason isnt ive got a lfor me. Thats why i got my surface. Its great for watching game film and drawing up plays. Its got onenote, so i can stay on top of my todo list, which has been absolutely absurd since the big game. With skype, its just really easy to stay in touch with the kids i work with. Alright, russell you are good to go alright, fellas. Alright, russ. Back to work engineers build, farmers grow, artists create, but teachers, they do it all. They build minds, they help children grow and they create leaders. Make an impact on a childs life. Get into teaching. The more you know. Alex mueller was alone at his familys vacation cabin in colorado. His sisters werent on this weekend trip, and that saturday afternoon his parents went out for a hike without him. Do you remember the last words reporter just a normal, like, of course im going to see my mom in an hour. Yeah, exactly. I mean, nothing really memorable. Reporter and so then theres a whole period of time that theyre gone. Whats the next thing you remember . So reading, kind of hanging around. I think the first time i kind of noticed that it was getting a little late, it had gotten dark and, you know, nobody should be kind of hiking or Walking Around when its dark. Reporter alex had no inkling of the tragedy unfolding at Cottonwood Creek. It started right after his dad took this picture of his mother, leslie. Leslie and gracie posed here. You can see its a stunning setting. But just about an arms length behind me is a cliff. A steep drop off to the granite below. And the icy cold waters of Cottonwood Creek. Right after fred snapped the picture, leslie fell and was swept away in the water. Unable to find her, fred raced for help, driving more than a mile to the nearest house. Somebody just showed up at my house. Reporter with no cell service up by the creek, the owner of the house, justin sparks, was the first to call 911. He pulled up, he said, at the waterfall. Shes in the river. She fell and they cant find her. Hes frantic, of course. He said he thinks his wifes dead. Its his wife . Yes. Reporter the homeowner offered right away to help fred. They sped back up the mountain, and fred dropped him off at a spot to begin searching. Just down the road, physicians assistant and ems volunteer Michael Golub was on duty. A call went out over the radio for a female drowning victim. Reporter golob headed over to the base of the trail. There he ran into fred. He comes barreling down at a very high rate of speed to kind of slams on his brakes and starts yelling at me, lets go. Lets go. Lets go. Reporter the ems responder noticed this man he was trying to help could also be injured. Freds face was scratched up. He has some superficial lacerations. And so i take a minute to make sure this isnt my second victim, to make sure hes okay. And he assures me hes fine, hes fine, just kind of wants to keep going. Reporter but then as fred drove, he seemed disoriented. He pulled over, but he couldnt seem to find where leslie fell. I start to unload from the jeep. He says, no, this isnt it. And we get back in the jeep and he continues upstream or uphill. Reporter after another stop, they found the right place and hiked toward the creek. All of a sudden, i hear yelling and the yelling is coming from downstream. Reporter it was the homeowner justin sparks. Michael golub took off toward him. He was in a kneedeep pool down below the waterfalls. There was mrs. Mueller. Shes dressed in a lime green jacket. And shes floating face up. He actually found her. I believe he used the word pinned under the log and face down. Reporter leslie had no pulse. But golob thought there was still hope that she could be revived. Fred had caught up, towering over them from the creek embankment. He says, is she dead . I tell him its too soon to know. Reporter golob sent fred back down the road to look for more help. By then, a small village of First Responders had assembled at the start of the trail, among them was Hinsdale County sheriffs Deputy Justin casey. We had other officers responding, that we also had the e. M. S. Personnel coming in ambulances, and we had fire personnel coming with the fire trucks. Reporter dispatch put a call into the local sheriff, ron bruce. We had gotten a report of a drowning up on Cottonwood Creek. And they said theyd keep me advised. Reporter and this probably didnt seem totally out of the ordinary for you. No. cause we reporter up here . Weve had them before. Reporter people fall on when theyre just simply hiking, they break something. Reporter and some people die up there. And we have to retrieve the bodies. Reporter by then, a group of medical responders made their way up to the creek to help. But still, no heartbeat, not a breath from leslie. And it was clear she was gone. We were not going to be able to bring miss mueller back. Reporter at the cabin, alex was wondering why his parents werent back yet. Their hike was only supposed to last an hour or so. But theyd been gone more than three hours. Were you worried . Not really worried, as in something happened to them. Just more like its kind of weird that they would, you know, stay out past dark, if theyre going for a hike. Reporter it was past 8 00 p. M. When his dad got home without his mom. Its my dad and the deputy, and yeah, they come in. Its kind of a shock to see, you know, when youre expecting somebody, to see strangers coming in instead. Reporter what do you think when you see that . Not a whole lot of time to think, honestly. You kind of go into shut down mode. Reporter alex recalled his dad seemed like he was in shock. He was very disheveled, had been crying a lot. And then he, you know, gave me a big hug, and that was kind of how it broke. Reporter i cant even imagine getting that news, when youve just thought your parents were going for a quick hike. Just kind of disbelief, really. The whole thing just seemed so surreal. Reporter then father and son were shuttled to the Sheriffs Department where fred could file a report about the accident. I remember them saying, you take fred, ill take alex. Reporter sheriff bruce was at the station to meet them. My initial reaction to fred was he was a victim, a grieving husband. Reporter fred gave a brief, handwritten statement. We want to make sure weve dotted the is and crossed the ts. We were dealing with the death of a woman. Reporter then fred and alex headed back to their empty cabin. And there, in that home that had until then been full of such happy memories, fred and alex endured the longest night of their lives. We stayed together in the same room the whole night. Reporter and did your dad sleep at all that night . It was a very long night. Reporter but they had no idea it was just the first sleepless night in what would become the longest ordeal of their lives. Coming up, fred gives investigators a detailed account of what happened to leslie and he is very clear on who is to blame. It was that dog tangled up in her legs. What would police think of that . release of steam chug, chug of train on tracks bellow of fire from dragon background cheers from patrons on ride coaster rolling over tracks the adventure youve been dreaming of. Is here. The Wizarding World of harry potter, featuring the all new diagon alley and the hogwarts express. Come and live it. thunder crash universal orlando resort. Ice cream ice cream ice cream ice cream [ chuckles ] [ singsong voice ] for you. Yeah, that ice cream man has nothing on us. Its not even a competition. Thank you, walmart. [ chuckles ] [ male announcer ] more ice cream, more summer fun. Walmart. So safely whiten your smile with listerine whitening®. Other mouthwashes just whiten teeth. But only listerine whitening® both whitens and restores enamel. New listerine whitening vibrant®. Power to your mouth. The ambulance racing by you. The ambulance chaser. Chasing the ambulance. A rollerblader with headphones whos oblivious to everything. The cab driver whos checking out the rollerblader. Its 360 degrees of chaos out there. But with driverassist technology, including a blind spot system and a rearview camera, the ford fusion will help tell you when its coming. The ford fusion will help tell you when its coming. Teacher layoffs. And a 60 billion dollar budget deficit. Thats what john perez faced when he became speaker of the california assembly. So he partnered with Governor Brown to pass three balanced budgets, on time. For the first time in thirty years. Today, the deficits are gone and weve invested an additional 2 billion dollars in education. Now john perez is running for controller, to keep fighting for balanced budgets. Democrat john perez for controller. Fred and Leslie Muellers daughters, amanda and ariel, were hundreds of miles away from colorado when it happened. Their dad had to break the terrible news to them by phone. He said, im so sorry. Im so sorry. And i said, what happened . And he said, we were hiking. I was trying to take a picture. She fell. And i remember saying, but shes going to be okay. And he said, no, shes dead. And i kind of lost it. I started crying terribly. And he said, im so, so sorry, mandy. Reporter what did your dad say to you when you got him on the phone . I dont even think i asked him what happened, because you dont want to hear details. I mean, i could easily say that was the worst day of my life, that i found out about my mom. And the only detail that matters, that she was gone. Reporter the tragic details, however, were the business of Hinsdale County sheriff ron bruce. He and his small office have the huge job of patrolling more than 1,100 square miles of potentially dangerous wilderness and wildlife. Should they have not gone oh no, no. Reporter to that area . Or was it okay . It was perfectly fine. I think it he related it was something of an idyllic day. Reporter the day after leslie died, sheriff bruce stopped by the muellers cabin to get a more precise account of what happened during their hike. Bruces undersheriff and a state investigator talked to fred. You know, i shouldnt have even taken her up there. Its all my fault. Reporter the conversation at the muellers Kitchen Table was recorded. We started taking photos. She took a few of me. I took some of her. Reporter fred described in detail how that kodak moment went wrong. I suggested that she take a picture with her dog, and its a Border Collie and its a very its just extremely skittish dog. She looks at me and i take her picture and we think everythings cool and i think like a bird kind of flutters by. Reporter fred said the rambunctious Border Collie got startled. But the dog just jumps out as shes turning and its like its like her feet just went out from under her. Its like its just happening in slow motion in front of me. She falls forward and i remember lunging forward to try to get to her, but i was probably five, six, seven feet from her. Reporter fred said he witnessed leslie free fall. It looked to me like she just did a swan dive. And la