reporter: and it was what he saw the man do that told de jong the woman was dead. he really slammed her. and then you don t start hiding this person in the crawl space. reporter: joran van der sloot is serving 28 years in prison for the murder of a young woman in peru. he s never been charged in the natalieee holloway case. now de jong s testimony seems to practically solve the mystery of what happened to natalee, and nearly ten years after she disappeared, authorities have finally got around to investigating it. i don t know if he s lying. i can only say that his statement can t be true. reporter: that construction site in 2005 is now a 12-story vacation report owned by marriott. and the prosecutor says marriott informed him at the time natalee vanished there was no construction. because when there s no