Transcript for One of two men hired by man who planned his family's murder confesses to cops: Part 4
Call, visit, or go to xfnitymobile.com. Reporter: Cerralvo, Mexico. A tough little town about 50 miles south of the border. Legend has it, mobster Al Capone once hid out here, and if it was good enough for scarface, it was good enough for another American stranger who suddenly showed up here looking for work -- and a new identity. Translator: He caught my attention because he was different. He was a white guy. It was a very unusual thing because you don't see workers -- American workers -- right here in a little town in Mexico. Reporter: Osvaldo Benavides and his close friend Ubaldo Salinas quickly accept the likeable man who says his name is Rudy Rios. He tell me the name was Rudy. He was a nice person. So this guy, Rudy, of course, is made up. He was a person, an identity concocted by Bart Whitaker. He didn't tetold us that he was a soldier. That was my legend down there. I was a soldier that was awol because I had been shot up and didn't want to go back. That was told from the very first minute I was down there in order to cover me. ??? Reporter: Posing as Rudy Rios, Bart begins turning up at church, and turning on the charm for a guitarist he meets there -- Sindy Lu Salinas. Translator: He would bring me flowers. "Look! I brought you flowers!" I thought he was so handsome and -- I don't know -- mysterious. Reporter: She brings her new boyfriend home to meet her parents. He's an immediate hit. Her father, homero, even hires him to work at the family's furniture store. Translator: I ended up loving him like a son. Very, very much. ??? Reporter: Sindy Lu knows nothing of her boyfriend's true identity. But one night she gets a terrifying glimpse. It's what he says while consoling her after she smashes her guitar during an argument with her mother. Translator: He said, "No, relax. Let's fix things." He said, "Don't be angry at your parents. If you want we can kill them." So I told him "No, but it's not a big deal. And that's the only time I felt a bit of fear, but I know maybe he said that so I would calm down, or to get me to laugh. Reporter: But no one was laughing. Certainly not back in Texas, where even Kent Whitaker was now beginning to believe the worst. When he ran away it kinda kicked the third leg out of the stool, that he must actually have been involved. By that point in time I'm thinking it's pretty hard for me to extend any potential arguments against it. Reporter: But investigators still had no physical evidence, no clue who fired the murder weapon, and no idea what happened to Bart Whitaker. I had nowhere to look for him and no leads to follow up on to try and find him. So that was disappointing at times. Reporter: The investigation is cold, until a big break from two men who knew Bart while he was pretending to be a college student. Almost two years after the crime occurred, Steven champagne called me. Steven champagne was a marine in 2005, but back in 2003 when the murders occurred, he was a bartender. He worked with Bart Whitaker at the country club up near lake Conroe. Reporter: Now champagne was pouring out secrets about himself, and Bart's roommate back then named Chris Brashear, two aimless guys at the time who were ripe for a payday. Bart promised them if they'd help him pull off an outrageous scheme. And when they came in the house Chris was to shoot 'em all. That was absolutely the break we needed. Reporter: Champagne gives up the entire story of what happened on the night of December 10, 2003. What was Bart's part in the plan? He pretty much set it all up. How did you know which restaurant? Bart had told me before they left. Reporter: As the whitakers unknowingly celebrate Bart's bogus college graduation at a popular cajun restaurant, Steve champagne watches from the parking lot. Meanwhile, Bart's roommate Chris Brashear hides in Bart's SUV outside the Whitaker home. At that point Chris got out of the vehicle and entered the house with the key and the alarm code. Did you see them leave pappadeaux? Well, yeah. So then I pretty much followed them home. They pulled in the driveway and I just kept going just around the block, you know, one block over. And then in a minute, Chris came walking, like, out to the car, got in the backseat. He said Bart's brother had walked in first. And, when Chris shot him -- he said before he shot him he thought he smiled. And then Chris shot his mom and then shot Bart's dad in the shoulder. And then, he acted like he wrestled around with Bart and shot Bart in the shoulder. You could characterize that interview as chilling. I don't think there's anyone who could watch that and not wonder how a person could be so cold. Reporter:ware of champagne's confession, Chris Brashear agrees to an interview -- but quickly becomes very uncomfortable. I'm just gonna go. Is that all right? Yeah. There's the door. Reporter: So sergeant slot, Steven champagne's confession yields the one thing that links this trio to the crime. He mentions a key piece of evidence that only the police knew about -- a single glove dropped by the shooter, found beside Bart's SUV. He knew about the missing glove. And, obviously, we had this glove in evidence already. So everything fit together just based on one small piece of evidence. Reporter: But sergeant slot still has no physical evidence to link Bart to the murders -- until now. Steven champagne explained to me that he and Chris Brashear had thrown items from the crime scene into a bag and thrown that off of a bridge that runs over lake Conroe, near Bart's town home in Willis. Reporter: Down below, a dive team discovers a duffel bag. In the soggy bag, a treasure trove of decomposing evidence. It's a windfall for crime lab investigator max hunter, beginning with an innocuous-looking plastic water bottle. You just go around the rim of the bottle. Reporter: And even after two years in the bottom of a lake -- They were able to obtain a DNA profile. From that swab, and that DNA profile matched the DNA profile for Chris Brashear. Reporter: Among the other items in the bag -- a rare brand of ammunition identical to the fatal bullets. A glove that matches the one found at the crime scene. A pry tool that matches the marks on the whitakers safe. And a badly damaged cell phone. A lab in England identifies Bart Whitaker as the owner. Finally, sergeant slot has the physical evidence he needs to link Bart to the murders. This is definitely when we said, "We've got it." Reporter: But where is Bart Whitaker? Sergeant slot obtains an arrest warrant, but he does not know that Bart -- now known as Rudy Rios -- is hiding in Mexico. And then, the biggest break of all -- a phone call from the real Rudy Rios -- when we come back.
This transcript has been automatically generated and may not be 100% accurate.