Transcript for Dad survives son's murder plot that killed mom and brother: Part 2
Reporter: Texas death row. On the surface, Bart Whitaker seems intelligent, well mannered, the son of an affluent family. So it seems inexplicable why this quiet young man awaits execution for an unthinkable crime. You were raised by a loving family. Uh-huh. Your mother loved you. Your father loved you. Your brother loved you, yes? Yes, ma'am. But you still decided to kill them. I did. Reporter: A heinous crime committed on a whim says prosecutor Fred felcman. With Bart Whitaker, there's no reason why. He just wanted to, and that's what's scary about it. He didn't need their money. He didn't need their love. They had never done anything to him. He just wanted to do it. Reporter: On the night of his graduation dinner, Bart charmed his family, playing the role of the gracious man of the hour, or was he? You're smiling in this photo. This is like a half-hour before your family is going to get gunned down. What were you feeling in that photo? I was about as close to numb as a human being can get, I think. Reporter: It was just after 8:00 when the Whitaker family leaves the restaurant, and Bart's secret murder plot is unfolding as he expects, just as he and his unwitting family arrive home. The Whitaker family suspects nothing, but as they enter the house, Bart hangs back. I'm on the front porch and, uh, I hear a shot, and then Trish is saying, oh no, and then another loud noise, but I know you don't -- can't quite imagine this, but I didn't recognize them as gunshots. I didn't really understand what was happening. At the time, what were you feeling? Nothing. Nothing at first, and then the gunshots went off and shock. I walked up to the door. All the lights in the house were out, but the street light showed a single figure in a ski mask maybe six, eight feet away. My reaction was I wondered which one of Kevin's goofball friends is playing a trick on us with a paintball gun, and I just stood there, but a moment later, I was shot too. And before I could call out to see how -- if Bart was safe, there was a fourth shot from inside the house, and my reaction was, my god, he shot all of us. Why? Reporter: As shots ring out a neighbor calls 911. Someone's just shot my neighbors! Get over here! I know I ran into the house. They say I ran past my dad, but I don't even remember seeing him. Do you remember getting shot? I do vaguely remember making the 911 call. I've been shot. Where have you been shot at sir? In my arm. Okay Bart, who shot you? I don't know. That he went out the back door. I think I said that. I pulled up about three houses down, and I pull my weapon, and I start running through the yards to get to the Whitaker house. Reporter: First on the scene, Sugar Land police officer Phil Prevost finds 19-year old Kevin Whitaker dead where he fell, a single bullet in his chest. Tricia Whitaker also dies of a single gunshot wound soon after she's airlifted to the hospital. Incredibly, Kent Whitaker survives the attack shot in the dhes chest. Also wounded, Bart makes for a convincing fourth victim. Where are you in the house right now? In the living room. Okay. Do you see the officers, Bart? Yeah. I asked him. I said, who are you? Who are you? And he said, I'm Bart. He said, I live here. This is my house. So I figured he belonged there and said, where's the bad guy? Can you tell me anything about him at all, Bart? Did he sound black, white, hispanic? Maybe black. You had yourself shot as part of this plan. Was that your idea? Yeah. It was to distance me from the guilt. So you were trying to throw the cops off, in your mind. Yeah. Reporter: And it works like a charm. The crime scene that I was investigating was a burglary gone bad where the victims were shot by the suspect, and the suspect fled the scene. Reporter: Homicide sergeant Marshall slot thinks he's looking for a burglar with bad timing. We called out tracking dogs that night to -- in an attempt to track the shooter. Reporter: The dogs pick up a scent in the house and follow it outsidto a dead end. Sergeant slot scans the crime scene for anything that might lead him to the killer. He finds drawers pulled open as if by a burglar. A gun safe, pried open. Four spent shell casings, and on the kitchen floor, a 9mm handgun with four bullets missing from its clip. Investigators find no suspect fingerprints at the scene. They take the gun back to the crime lab for a closer look. Initially it was processed for latent fingerprints. Reporter: Investigator max hunter carefully tests the weapon and makes a hopeful discovery. A partial latent fingerprint was developed on the left side of the slide. It was a partial palm print, but, that palm print did not have enough information in it. We couldn't identify it to any one particular person. Reporter: Tracking dogs identify the shooter's scent on the gun, but DNA analysis comes back negative. It seems the killer made a clean getaway. It seemed like every piece of evidence that we collected, we ran into dead ends left and right. Reporter: Back to square one. Sergeant slot and his partner detective, Billy Baugh go to the hospital to interview the survivors, Kent and Bart Whitaker. They were in separate rooms. So we first went to Kent Whitaker. Kent seemed somewhat at peace. He was obviously upset, but not crying, but he very much demanded that we catch who was responsible for committing this crime. Reporter: Lying in his hospital bed, Kent Whitaker is torn between emotional extremes. He wants revenge, but he also prays, asking god to give him the strength to do the impossible, and forgive whoever was responsible. And the moment that I did ask him to help me forgive, the strangest thing happened. This warm glow flowed over me just instantly, and I looked at my heart, and I realized that that desire for revenge had gone. Reporter: The thought that it might be his own son he would need to forgive was the furthest thing from Kent Whitaker's mind. When he told me that he had forgiven the shooter I was shouting inside, well, what if that's my fault, and I -- of course I didn't have the courage to say anything at the time. How do you face that? I don't know how to face that. Hiding it all from everybody else was sort of like hiding it from myself also. There's also the fear of this ace, you know. Reporter: All of Sugar Land seems stricken with grief and outrage. More than a thousand mourners, including Kent and Bart, attend the funeral for Tricia and Kevin. At the Whitaker family home, it's a media circus. Get away from me! Reporter: With the vestigation hitting dead ends Bart has good reason to believe he'd gotten away with murder, but when we come back, the huge secret he couldn't allow his family to discover? How could he be so stupid? I just read him the riot act about how if he had been telling the truth he would not be a suspect.
This transcript has been automatically generated and may not be 100% accurate.