Police question ex-boyfriend of slain Texas doctor's girlfriend: Part 3

The alibis of Mike Dixon, Richelle Shetina and Joseph Sonnier's ex-girlfriends all checked out, but police have a breakthrough after a tip from a man named Paul Reynolds.
6:29 | 03/09/19

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Transcript for Police question ex-boyfriend of slain Texas doctor's girlfriend: Part 3
in his house. It looks like a burglary. There's nothing stolen. One of the things that we're trying to establish is, okay, why is doctor Sonnier dead? The crime scene pretty much is a little disorganized. And there was evidence at the crime scene that suggested it was a hit. I'm not dealing with a professional hitman. So we have to figure out, okay, what's going on in this man's life? We talked to Richelle. All of a sudden we may have a reason why it all kind of came together, and he was murdered. Richelle, having told detective Johnson about her former boyfriend immediately sent up red flags. Was there somebody else, part of this whole craziness? He's Dr. Thomas Michael Dixon. He's a plastic surgeon in Amarillo. Hello. I'm Dr. Mike Dixon. So you have this information from Richelle, could've been Mike Dixon. So I'm still trying to figure out what's going on. And I knew, well, we're gonna get a little bit more insight into this thing, we talk to doctor Dixon. 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. And I was like, okay, well, that's a little odd. Because in our interview with Richelle she told us that he knew about the relationship. I'll be honest with you. I loved, loved, loved that woman. I really did. He was obsessed with Richelle. He was having a lot of problems getting over this breakup. He just couldn't seem to let her go. I really had fallen head over heels. In fact, made a lot of life changes for her. We've learned that he's already had a divorce as a result of this affair with Richelle, but he's not quite over her yet. You know, I've learned that he -- he still loves her. He's got a lot of feelings for her. He's very upfront about, "Yeah, I wanted her back." There probably was a very close relationship there between Mike Dixon and Richelle shetina. They grew apart because Mike wasn't interested in marriage. Richelle seemed to think that at one point Dr. Dixon was probably going to propose to her and there was a build-up leading to her birthday. And she thought it was coming and maybe there's a ring. And instead, it's a subscription to the tea-of-the-month club. And she went ballistic, and said it isn't -- I remember it clearly. "It's not a big Rock." I said, "No, it's not." Like, a wedding ring. When Dixon talked to police he talked about how he gave you this tea of the month club birthday gift and it really, really angered you. It wasn't about the fact that it was tea. Tea is lovely. I don't happen to drink it. It wasn't the gift that upset me. He could've shown up at my doorstep and given me a hug and said, "Happy birthday. I'm so glad to be here with you today," and I would've been the happiest girl in the world. He was not present in any emotionally supportive aspect of my world. Despite the breakup between Dixon and Richelle, they stayed in contact with each other. They texted. They went to dinners together, and they even planned a weekend getaway. She was like, "Hey, do you want to put this back together?" I was like, "Yeah." I did. "Let's plan a trip," blah, blah, blah. They had agreed to go on a trip. All she had to do was go up there. The next day, she's like, "Hey, sorry. I'm in love with my dance partner." Okay. I was like, "Really?" Boom! She drops the hammer on him, and says, "Oh, by the way I'm in love with my dance partner." Some would say, well, you're throwing it in his face a little Well, no. I wasn't throwing it in his face. There was, you know, an ugliness from him to me. It's, like, you know what, if you want to have a getaway, enjoy it. Go. Enjoy your getaway. I don't wanna be a part of it. After Richelle ended the relationship with Dr. Dixon, he started dating a medical student who was a couple of decades his junior. This young medical student, Ashley woolbert, actually happened to be his alibi because they were having sushi the night of the murder at a restaurant in Amarillo. What has he told you about Richelle? Just that she was his exgirlfriend and that she was really pretty and they dated. Him and his wife were separated when they started dating. Johnson is just stumped. The alibis of Mike Dixon, of Richelle, and of Dr. Sonnier's exgirlfriends'they all check out. There's still the stalker that Richelle thinks is following her. This big, burly man that Richelle saw in the backyard. There's something not right here, but that's all that I have. This is a huge whodunit. What was it that broke this case wide open for you? When Paul Reynolds called the police department. My name is Paul Reynolds, and I think we've got a crime that happened down here in Lubbock. It's a homicide. Who is Paul Reynolds? Believe it or not, there are good people in the world and Paul Reynolds is one of them. He was scared. Paul Reynolds is an aspiring nurse who's fallen on hard times. He's crashing on the couch of his friend in Amarillo, who tries to commit suicide by cutting his wrists and taking pills. Then that friend starts talking about murder. I'm staying with this friend of mine. He said he went down there. He said he shot the guy. What is your roommate's name? His name is Dave Shepard, s-h-e-p-a-r-d. That was a name detective Johnson had heard before. We have Dr. Mike Dixon. We have Paul Reynolds. We have Dave Shepard. He's quick-witted, I'm kind of sassy .

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

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