Texas doctor found shot and stabbed to death in his own home: Part 2

Police questioned Sonnier's girlfriend Richelle Shetina, who told them about her ex-boyfriend Dr. Thomas Michael Dixon.
7:51 | 03/09/19

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Transcript for Texas doctor found shot and stabbed to death in his own home: Part 2
911, what's the emergency? Somebody has broken a window in the back and the doctor did not show up for work today. On a hot July morning, Joseph Sonnier was found dead in his home. Oh, no! Oh, god! Ma'am? Ma'am, what's going on? His landscaper found him shot and stabbed multiple times. There's a bullet that was laying on the ground! I need somebody to hurry! Yes, ma'am. Zach Johnson, a homicide detective with the Lubbock police heads to the scene. Dr. Sonnier's neighborhood, what kinds of crimes would typically happen there? In my experience it's been residential burglaries, prowler calls, suspicious persons. Stuff of that nature. It's not murders. Not murders. Not violent crime at all. This neighborhood had to be freaked out by this killing. They were. They were very scared. Because this doesn't happen, especially to somebody that's so esteemed. When I first covered this case, detective Johnson took me to the crime scene. As soon as Zach Johnson walked in to the house, he knew immediately that this was not a robbery gone bad. There was artwork in the there were very expensive pieces of furniture. There was iPads, all kinds of things, just kinda laying around. You know? Nothing was taken. It was an in-and-out job. Whoever came in this house came in to kill the doctor. In the dining room is an initial scene where you have the windows pushed in and you have a trail of blood. And that crime scene was very succinct. It wasn't spread out. You had the overturned chair. You had the glass on the floor, and you had the casings. So, you knew that he was shot right here. The investigators see a Gatorade bottle and a shell casing with a hole blown out of the Gatorade bottle, suggesting somebody came up with the idea of a crude silencer, which I can tell you doesn't really work. We were dealing with something that was a hit, you know, of sorts. That somebody had come to this house to kill this person specifically. To me it was just mind-boggling. You know, why is this man dead? He's a well-respected citizen in this community. Why is he dead? The Sonnier children were devastated. I mean, first, their mother is murdered. Then, their father is murdered. This just doesn't happen. It doesn't happen. Forget about the coincidence of it all. The statistical likelihood that both parents would be murdered on separate occasions is unfathomable. I got the call the day before the two-year anniversary of my mother's death. I thought maybe it had something to do with her death. That's how out of left field and completely out of nowhere this was. We started racking our brains. Well, it's gotta be some type of girlfriend situation. If it's not a robbery, it's somebody he knows. His housekeeper, Fran, called me. She said that something was going on at Joseph's house. The police were there and they wanted me to come down. When something like this happens, the first person police talk to is the closest loved one and that would be Richelle shetina. I was in shock. I was devastated. Meeting with Richelle that very first time, I don't know a lot about her. In the very beginning you always have to consider people the closest. Because 90% of the time it's going to be the people that are closest to our victims that commit the crime against them. How would you describe your relationship with Dr. Sonnier? He's the love of my life. There were a couple of things that were mentioned by her that struck me as odd. Richelle shetina had felt a little uneasy in the previous weeks before the murder took place, that someone was watching her. Maybe she was being followed. Something didn't seem quite right. I had gone in to work out, and I pulled into the parking lot. There was this big, creepy-looking guy sitting there. He was at the door, like, he was looking for someone or watching someone. It gives the -- you know, the investigators another, sort of, perspective as is there some sort of surveillance or somebody that's actually watching the doctor and Richelle? It was dark outside, and Joseph and I both saw a flash from the outside. We laughed and kind of joked about, you know, maybe somebody was following us. Right from the beginning, Richelle's attitude is pointing the fingers at all kinds of people. She starts offering a laundry list of potential candidates. There's just, you know, some girls that he dated. Joseph would get these horrible text messages, you know? Calling him a . You know, you're such a And whatever. Reporter: Richelle starts telling Johnson about different ex-girlfriends in Joseph Sonnier's life as people who could possibly hold a grudge against him. I got a letter in my mailbox and it was from this girl who said that she met Joseph on the internet and that they had sex for money, basically. And he said, "You know, this is obviously someone trying to drive a wedge in between us." Was there a sense of who might be trying to drive a wedge between the two of you? To me it was, like -- it had to be, like, an ex-girlfriend or something. But Johnson has an idea that maybe someone in Richelle's past that has it in for Dr. Sonnier. So there could be somebody that you think we need to look at? A couple of people. Okay. Tell me about one of them. Dr. Thomas Michael Dixon. He's a plastic surgeon in Amarillo. Hello. I'm Dr. Mike Dixon. If you're considering surgery -- He had a med spa in Amarillo. And I went there to get Botox injections. What attracted you to him? He was funny. He was very witty. You know, he was enjoyable. If it can be enjoyable to have somebody put needles in your face, you know, I guess that's about as enjoyable as it could be. Richelle and Mike Dixon had dated for about a year and a half, and then they broke up. And then, Richelle started dating again, soon after, seeing Joseph Sonnier. Did he know about your current relationship? He knew I was dating Joseph. He called him by name in a series of text messages trying to get me to go out with him, to meet him for coffee. So he wanted you to see him on the side basically? He wanted me to come back to him. I told him no. But the real question is, was Dixon the kind of man to take no for an answer? Johnson wants to know what Dixon knows. So he jumps in his car and drives two hours to Amarillo, Texas to talk to Mike Dixon, secretly recording him when they Hi, I hate to come bugging you at your house at all hours of the night -- What's going on? Well, we've had a homicide in Lubbock, Texas, today. I told him it was Richelle's boyfriend. And his first thing was, oh, well, I don't know anything about him. I don't know anything about him. I haven't talked to her in months and months. Zach Johnson knows someone is lying.

This transcript has been automatically generated and may not be 100% accurate.

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