Transcript for Searching for Clues in Ashes of Murder Victim's Life
"20/20" continues with the burning bed. Once again, Jim Avila. Reporter: As Lucy Johnson's house on hidden meadow court smolders, Gaston county, north Carolina, police are feeling the pressure. A nurse and caring mother of two with another baby on the way, her badly scorched body found atop her burning bed. The police interrogation room needs a revolving door with the long list of exes, from two husbands, a former boyfriend and the fiance. To question. Which way to turn? Everyone is watching. Including local TV reporter ken lemon. The thing that I think really drew people in is that you have a single mother. And she was excited about her, you know, relationship and her engagement with this man. Reporter: Where would the evidence lead police? First, a quick search of the house, shown in this police video, seems to rule out a stranger. No evidence of a break-in here. The locks are still intact. She was killed in her home. That's a total violation. And the belief is that she was killed in her home by somebody she knew. Not by a straunger. Reporter: Next, police move to the autopsy sketch. The medical examiner must have worn out his pen illustrating the terrible damage. And there, inside Lucy's head, a find that will change the investigation -- a bullet. And then more. Fragments of a second bullet. Conclusion? Lucy was shot twice in the back of the head. Now, it's not only an arson case -- now, friends, we have a murder. The very public search for a killer is on. And local media is watching. So many questions today about a fire that took the life of a pregnant mother. We have several people of interest that we're looking at right now. So everybody's watching. People wanted to know who did this. Reporter: Another clue from the crime scene -- the burned out house. Lucy's engagement ring can't be found anywhere. But also missing and perhaps even more important is a murder weapon. Where is the gun? Dive crews are back at lake Wylie looking for evidence to solve a pregnant mother's murder. Reporter: They target an area near a boat landing not far from the home of a potential suspect, Lucy's ex-boyfriend Jim spelock. Two days of diving for a weapon didn't produce anything. Reporter: There's no weapon. There's no gun found. There's nothing. Reporter: With no fingerprin, everything destroyed in the burned-out house, no murder weapon and no eyewitnesses to the crime, police must now turn to the circumstantial clues. Starting with the men in Lucy's life. Lucy's uncle, ken dye, saw them come and saw them go. She made some men angry. She -- yes. Reporter: Gaston county police open up the interrogation room. They bring in Phillip okrulica for questioning. He's Lucy's first husband and the father of her daughter Lauren. When they were together, okrulica was arrested for domestic violence twice. He comes in to tell police he never really hit Lucy, but he did grab her. But that trail cools when okrulica has a tight alibi. The night of the fire, he says he was home all night, and his new wife confirms it. Onto Lucy's husband number two, Jim Johnson. Another relationship that got ugly at the end. He has a police record of violence against Lucy, and Lucy's friend Deana says she witnessed one incident. He had her cornered in a corner, drilling her like a sergeant. Barking at her verbally, loud. She was afraid. She was very afraid. He was a suspect because he had threatened to burn her house down. Reporter: That's a pretty good reason to be a suspect. Right. Reporter: But more investigation shows Johnson was on the Carolina coast, four hours away at the time of the crime, forcing police to dismiss him as a suspect. So, now we turn our attention to Mike mead, Lucy's new fiance and father to be. Mike and Lucy's romance was so recent, that day at the fire was the first time her uncle ken dye had ever seen him. I didn't know who he was, never met him before, didn't recognize him. And then, I noticed that the detectives put him in the car and was talking to him. Reporter: But of all the stops on Lucy Johnson's troubled trail of romance, one man stood out. At least to family and friends. Oh, yes. At the very, very beginning I thought Jim spelock had did it. Everyone did. Reporter: James spelock, the father of Lucy's infant son, is in the family's crosshairs. Lucy's father, Mike dye. That Killed my daughter. Reporter: Ken dye says his mother, who raised Lucy from when she was a teenager, was convinced the minute she heard about the fire. She said, "I know who done it." I said, "Who done it?" He said, "Jim spelock done it." I knew immediately he did it. Something I felt in the pit of my stomach. Reporter: Why? Lucy's moving. She's marrying somebody that's going to be able to help her financially. Reporter: It is documented, spelock has been fighting with Lucy over child support and custody. Lucy has pictures of bruises on her arms and in family court claims spelock put them their while she was pregnant with their son. The relationship so poisonous, Jim spelock had been recording their conversations. You're a very sneaky manipulative person and it ain't going to work. No, you're the sneaky, manipulative person, Jim. I'm not. Because you're the one that did all of that. You're the one that was at the lawyer's office the day after I gave birth. I wasn't at the office I was on the phone with them. You're concerned with yourself. Reporter: That's Jim spelock documenting his attempts to see his son. Do you plan on paying child support voluntarily? Well, I guess that's up to you. Can I see my son or not? I've seen him like five times since he's been born. Are you going let me see him? Yes and you can bring me some money when you come see him. Reporter: Police want to know where spelock was the night of the murder, but he has plausible alibi too. He tells police he was at his house all night, with the baby. Did you stay here all night taking care of Cason? Yeah. I was here all night. Reporter: He has a roommate who says he didn't hear Jim leave. Then police find and interview this woman, who was up late, texting with Jim spelock most of that night. Did he text you Tuesday? He sent me the text at 4:30. Just want to make sure I have it all here. Reporter: But while the clues may be sending the family in Jim spelock's direction, law enforcement is not convinced. And when other people began to focus their coverage towards spelock, they were able to tell me early on, "Don't go there. Don't do that." Reporter: Police even issue a rare public statement clearing spelock on paper. It's unheard of. Police are going in a different direction and they make an arrest.
This transcript has been automatically generated and may not be 100% accurate.