Transcript for A brief, chance encounter between 2 women sets a dire plot in motion: Part 1
except it's all true. Council bluffs, Iowa, is a midwestern city with a small-town feel. It has many hardworking people who are willing to help their neighbors, friendly people. It's a quiet rural community. On the outskirts of the city, on the border near Nebraska, is big lake park. The park is huge. It's almost 200 acres, and there are Lakes, one filled with rainbow trout, hiking trails, and playgrounds. Big lake park was known to be a place that families frequented. It was very peaceful. But what happened here on a cold winter night in 2015 was part of a mystery that stumped police for years. On December 5, 2015, a woman was at big lake park taking an evening stroll. She'd gone to the park to think while alone on the walking trill in the dark. She took a seat on a bench to rest for a moment. She was approached by another She said a female approached her from behind, told her to get on the ground, and then fired a shot at her leg. She said the female ran off into the woods and then she felt it was safe, so she walked this pathway and called 911 because she had left her phone in her car. 911, what is the address of your emergency? I've been shot in the leg. Um, my -- my pant leg is filled with blood. Oh, Jesus. Is the assailant still nearby? I don't think so. I took off running. Do you know what she looked like at all? No, she was behind me. Council bluffs police responded. They had a helicopter over, could not find a suspect. This was a shocking event to have occur, but no one was able to find this woman with a gun running through big lake park. It's a mystery that started three years earlier ten minutes from big lake park in Omaha, Nebraska, with a man named Dave Kroupa. Dave krouas a 35-year-old mechanic. I was so fascinated by the fact that Dave Kroupa was just a normal guy, a really nice guy. He wasn't the kind of guy you'd expect to find in the middle of a murder mystery. My name is Leslie rule and I'm an author. Leslie rule was so intrigued by this story that she wrote a book about it calledngled web." For fans of true crime, her last name might sound familiar. Rule is the daughter of legendary true crime author Ann rule, who wrote the book "The stranger beside me" about her friendship with Ted Bundy. Rule is carrying on the family tradition. Dave Kroupa liked women. He made no secret about that, and he made no apologies. Dave Kroupa was recently separated from Amy flora, his long-term mate. They had two children together. They'd been together for 12 years. And he was on his own for the first time in a very long time. Dave Kroupa moved to Omaha in 2012. He got a small, kind of sad, single-dad apartment. And he got a job at an auto repair shop there. I didn't know how to venture back into the dating pool. I'd been out of it for a long time so I felt pretty rusty. I was sitting in an apartment by myself at the time with no furniture. So, internet dating was the thing. That was the way to go. The first person Dave met on an online dating site was a woman by the name of Liz golyar. Her full name is Shanna Elizabeth golyar, but she went by her middle name, Liz. Liz was a single mother with two children, and her kids were about the same age as Dave's kids. She had a business, Liz's housekeeping. Liz loved taking selfies and sending them to her friends. I thought was Liz was very pretty. I was attracted to her right away, so then we set up a date. Dave's first dates with Liz were at a coffee shop, and they just sat and chatted. She was sexy. She was bright and shiny, and she was very engaging. They had a lot of fun together. They got along really well. It was just a very casual thing. Dave was upfront. He absolutely did not want a commitment. He just wanted to have a little fun, and he was clear with every woman he met that that was the case. And Dave was starting to meet a lot of women. Mary. Cathy. Joyce. Beth. Margaret. Sandra. If the chemistry was there, and the woman was willing, Dave was more than happy to explore a sexual relationship. I was kind of going wild, just being free for the first time in a long time. But Dave's outlook on casual hookups changed. When he met somebody the old-fashioned way, face-to-face in a chance encounter. Six months after I met Liz, I'm at the counter managing the shop, and I'm the person greeting customers when they come in, and an extremely attractive woman walks in the door. It's a woman named Cari Farver. She brought her Ford explorer into his shop to be worked on. And she was beautiful, a lighthearted air about her. When we looked at each other there was a little spark. You know, we both smiled. You know, you feel that sometimes. Cari Farver was a 37-year-old single mother to a 14-year-old son. She was a computer programmer at a big firm in Omaha. She's showing me something inside the vehicle, and we're standing there, and we're very close, within a couple of inches of each other, and there's some tension. Cari talked to me about meeting Dave. And she was like, this guy, totally not my type, but there was just something there. Then, a few days later, he came across her profile on the same online dating site that he had used when he met Liz. So, Cari and I ended up going to Applebee's for our first date. We hit it off. As we're getting up to leave, I asked her if she wanted to come over and hang out. And she said yeah. So, we went back to my place, we shared a kiss, and then it got a little bit hotter and a little heavier, and then Cari stopped and said, okay, if we're going to do this, and this implying sex, that's all it is. You're not my boyfriend. I'm not your girlfriend. I felt like I hit the jackpot with that. I couldn't have wrote it better. One slightly awkward thing, the night of Dave and Cari's first date, Liz golyar came by Dave's apartment to pick up some things that she'd left there. I walked Cari out the front door, and she walked right by Liz, ay probably saw each for six seconds. It was just a brief encounter, maybe 10 seconds or less, but this encounter would go on to have lasting ramifications for all three of them. Cari didn't seem at all bothered by her encounter with Liz. In fact, she didn't even mention it when she visited with her friend, amber. She said that during the date she had fun and that she laughed a lot and hadn't laughed like that in a long time, and she didn't know what would happen, but it was working right now. Cari's job happened to be right around the corner from where I lived, versus an hour from where she lived. She had a big project coming up at work. She was working very late hours. Dave offered for her to stay at his house so that she wouldn't have to make that commute back and forth. I mean, at this point I've known her two weeks and she's got a key to my apartment. I was feeling pretty comfortable with her. November 13, 2012, Dave wakes up and gets rey for work, and about 6:30 A.M., he leaves for work for the day. I give her a kiss and I say, I'll see you later. When Dave said goodbye to Cari that morning, he had absolutely no idea the nightmare that his life was about to turn into. My phone starts blowing up with texts from Cari. "I hate you. You ruined my life." What is going on? I was blown away.
This transcript has been automatically generated and may not be 100% accurate.