"I know what happened to that girl," van der Sloot says in a secretly recorded conversation, according to a partial transcript of the Dutch TV show by crime reporter Peter R. de Vries.
"We're on the beach over there," he says in the recordings. "Suddenly, she wasn't moving any more."
"I've never discussed it with anyone. ... It isn't easy, either, not even now," van der Sloot says at another point. He adds that he was pressing for financial compensation from the Aruban government for his ordeal as a suspect in the case.
Since Holloway disappeared on May 30, 2005, according to the show, van der Sloot has lied to authorities, laughed at police and prosecutors, thrown a glass of wine in DeVries' face and boasted about his antics and alleged deceptions in conversations he thought were private.
Van der Sloot has said he was lying in his secretly conversations with Patrick van der Eem, a person he thought was a friend, but who was secretly working undercover for de Vries.
"It is true I told someone. Everybody will see it Sunday," van der Sloot said over the telephone on the Dutch television show "Pauw & Witteman."
"That is what he wanted to hear, so I told him what he wanted to hear," Van der Sloot said, adding that he never fully trusted the man to whom he'd described his encounter with Natalee Holloway.
"It is so stupid, it is so stupid, it is really stupid," Van der Sloot said, his voice cracking.
Based on de Vries evidence, the chief prosecutor in Aruba announced Thursday that he is reopening the case.
De Vries also showed his findings to Holloway's mother, Beth Twitty.
"She told me she kind of knew it already that Natalee wasn't alive anymore, but when you get this message it's still, yeah, a kind of relief," de Vries told ABC News.
Twitty admitted as much to ABC News' Chris Cuomo.
"Now, with the knowing," she said, "it lets you put some things to rest. And that finally, finally, finally it's over."
According to the DeVries Dutch TV special, De Vries built his case against van der Sloot with the help of van der Eem, an Antillian who spent his youth in Curacao and Aruba but who has lived in the Netherlands for many years.
Van der Eem says he met van der Sloot at a poker table in a casino, and they talked about starting a marijuana-growing business. The two later would talk about and smoke marijuana during lengthy conversations.
But van der Eem said he wanted to bring van der Sloot down and decided to set a trap. Soon, he approached de Vries, the famous Dutch crime reporter, about working undercover, and de Vries hired him.
"I knew what I was doing," van der Eem said. "I had no emotions for this kid. The mother deserves an honest answer for what happened to his daughter."
The mystery behind the disappearance of the blond teenager has eluded efforts by the Aruba police and even the FBI for more than two years.
De Vries showed some of the key pieces of videotape to the Office of the Public Prosecutor of Aruba Jan. 24. Thursday, the island's chief prosecutor, Hans Mos, announced he has "intensified [the] investigation of Natalee Holloway due to recently received information."
Mos had announced publicly last month that he had closed the investigation after an exhausting and often frustrating two-year probe.
"This information may shed a new light on the mode of which Natalee Holloway has died and the method by which her body disappeared," Mos said.
He credited de Vries with uncovering the leads and said, "This information may help considerably in the solution of the mystery of Natalee's disappearance."
De Vries said that he and his team had been conducting an undercover operation for five months.
Earlier this week de Vries released a conversation between himself and Mos after he showed police the evidence he had collected.
"Am I sitting opposite a happy man now?" de Vries asked Mos. The prosecutor is shown answering, "Now at least the truth is surfacing, and with that we can at least wrap up this case."
The Alabama teenager disappeared after a boozy night in an Aruban nightclub during a high school graduation trip. She was last seen outside Carols 'n Charlies bar with Joran van der Sloot, who is from the Netherlands, and the brothers Deepak and Satish Kalpoe, from Aruba. They have twice been arrested and released because of a lack of evidence. They have all denied any involvement in her disappearance.
According to the transcript of de Vries TV special, Van der Eem said he rarely pressed van der Sloot on the Holloway case early on – but van der Sloot occasionally talked about it anyway.
Following his arrest and release in December, the next month a hidden camera caught van der Sloot ridiculing the Aruban authorities that had just closed the Holloway case.
"They have nothing," van der Sloot told van der Eem. "I laughed at them, those investigators. … I didn't say a word. … I invoked my right to remain silent."
In January, De Vries' team launched a more ambitious surveillance plan involving a Range Rover outfitted with three hidden cameras and a tracking device, as well as several unmarked surveillance cars to observe van der Sloot and van der Eem as they rode around in the Range Rover.
And with the case dropped, it turned out, van der Sloot seemed to open up more about Holloway.
"Will they ever find her, do you think?" van der Eem asked, in one conversation.
"No," van der Sloot said.
"The only thing I still want is a big fat compensation check" for treatment by authorities in Aruba, van der Sloot added. "But before I have it, it'll be 10 years."
"But where … is she, Joran?" van der Eem asked.
"She'll never be found," van der Sloot said.
The day after that conversation, according to the transcript of de Vries special, van der Sloot and de Vries appeared together on a Dutch TV show, "Pauw & Witteman," on which de Vries offered theories on van der Sloot's involvement in the Holloway case, and van der Sloot, as he always has, publicly denied involvement.
"If it was proved that you were wrong, would you apologize to me?" Van der Sloot asked de Vries on the show. "Are you man enough to do so?"
"What do you think?" de Vries asked.
"I don't think so," van der Sloot said.
The anger escalated until the end of the show, when van der Sloot famously through a glass of wine in de Vries' face.
"The program was over and I'd just shaken his hand," van der Sloot told van der Eem on Jan. 13, according to the de Vries' transcript. "I look him in the face, and I shake that Pauw and Witteman's hands. … I see him looking my way, and I pick up that glass of wine … and I just throw it in his face. … And he goes, 'Ouch! My eyes! It stings!' And I was so cool. And then you see me going, calmly, like, 'Yeah, I thought you deserved it, you know.'"
De Vries offered another take on the incident.
"I was annoying him. I had questions and I was asking for answers, and he wasn't able to give me answers," de Vries said.
"He doesn't have complete control over his behavior," de Vries said of van der Sloot.
Twitty and Holloway's father, Dave Holloway, have waged a determined publicity campaign in an effort to keep the probe alive and find out what happened to their daughter.
Twitty has published a book about her daughter's disappearance and appeared on Oprah Winfrey's show in January in an effort to keep the search alive.
Police and even army units have combed the island looking for clues to Holloway's disappearance. The most recent search was carried out by oil drilling teams who volunteered their help. They used sonar to search the deep water off of Aruba's coast, but failed to find a trace of Natalee.
But on the tapes, van der Sloot offered what de Vries termed "nothing less than a straight-up confession" -- that he was with Holloway when she died and a friend of van der Sloot's disposed of the body.
"I know what happened to that girl," van der Sloot said, according to the transcript.
The investigative journalist Peter De Vries will talk exclusively about his investigation Monday on Good Morning America. That's on ABC 30, Monday morning, between 7 and 9 am.
ABC News is also airing a 90-minute special edition of 20-20 Monday night.
'The Final Hours of Natalee Holloway' will include all the details of the investigation. That will also air on ABC 30, Monday night at 9:30 pm.