And Bart seemed to share that anger. "He didn't say much. But he pulled my friend Matt and I to him and he said, 'We're gonna find who did it,'" recalls Kevin's friend John Flores.
Slot continued his routine questioning of the survivors. Bart told Slot he had just graduated from Sam Houston State University. But the next day, the detective says investigators got stunning news from the university: Bart wasn't enrolled.
"He was a freshman on academic probation," Slot explains.
The news made the detective suspicious. "Bells and whistles start goin' off that, 'Why is this kid lying to us?' 'What's he got to hide?'" Slot remembers.
The detective asked Bart why he had lied. Bart's response? Says Slot, "He just didn't want to disappoint his family. He had needed a break, the stress of school had gotten on him."
Then, just five days after the shooting, there was another bombshell. "It was about 11, 11:30 at night. The sergeant on duty paged me and said there's somebody here that wants to talk to you," Slot remembers.
Slot met the stranger in the darkened parking lot behind the police station. "He explained to me that he had information that was crucial to the investigation," Slot recalls.
The man told Slot that Bart wanted him to help kill his family.
Five days after Trisha and Kevin were gunned down at their home, more than 1,000 friends and family gathered to celebrate their lives.
Amid the sadness, there was also anger. "This murderer is still out there. Police need our help. For your own families for everyone's sake, let's catch him," a mourner said at the funeral.
But what no one knew was that among the mourners was a man police were closely watching: Bart Whitaker.
The stranger Det. Slot had met in the police parking lot turned out to be an old friend of Bart's named Adam Hipp. And he told the detective an extraordinary story: that Bart had approached him several years earlier with a detailed plan to kill his family.
"It called for Adam Hipp being the shooter, shooting the family members as they came in the residence," Slot explains.
According to Hipp, the plan even included a twist to fool police: Bart wanted Hipp to shoot him in the shoulder so he'd look like a victim, not a suspect.
"So what Adam Hipp was telling you was essentially the blueprint for what happened in 2003 … the real shooting?" Van Sant asks.
"The exact blueprint," Slot says.
But Bart appeared to have nothing to hide. He agreed to help detectives by re-enacting what happened the night of the shootings.
Bart's behavior at the crime scene only heightened Slot's suspicions. "Everything is very vague. It could have been this, but it could have been this," the detective remarks. "The fact that he wasn't able to give me a lot of detail on it, it was just unusual to me."
Police had indicated to Kent that his son Bart was a suspect in the case. Asked if he wondered if Bart might have actually been involved, Kent says, "I considered it but I didn't consider it seriously. He promised me there was nothing to it, that he didn't have anything to do with it, that he loved Trisha, Kevin and me. It was inconceivable."
But after Hipp's story, Det. Slot felt otherwise and decided to check out two of Bart's closest friends, Chris Brashear and Steven Champagne.
Brashear and Champagne worked with Bart at a country club just months before the murders. Slot asked them to provide what police call "scent samples." Using blood hounds, he compared those samples to evidence collected at the crime scene. Slot's hunch paid off when he got a match.
"The dogs indicated that Chris Brashear's scent was on the drawers that had been moved that night," Slot says.
More importantly, Brashear's scent was found on the gun used in the homicides.
When Slot grilled Brashear, he denied any involvement in the shootings. "We told him we had a definitive link between him and the murder weapon on the night of the shooting," Slot explains.
"What are you seeing on his face?" Van Sant asks.
"Horror. Panic," Slot says. "We struck a nerve with this kid."
Slot was now closing in on Bart.