It's a chilling insight into the mind of Joran van der Sloot in his own words. It's contained in the never-before-seen police files on van der Sloot, the long-time suspect in the disappearance of missing teenager Natalee Holloway in Aruba.
He's also accused of murdering another young woman in a hotel in Peru.
Writers Cole Thompson and Lisa Pulitzer showed INSIDE EDITION a document in which van der Sloot describes how he killed the Peruvian woman, Stephany Flores, during an argument in his hotel room.
"The lead detective said that when he looked into Joran's eyes, he saw a cold, calculated and evil person," said Thompson.
"I struck her head against the wall," he told authorities. "I had an impulsive reaction. She was strong. She bled a lot. Blood spilled on my clothing."
Van der Sloot later tried to retract the confession but the authors cite another damning document.
"His psychologist said that he's just prone to flying into fits of aggression, and when this happens, if he doesn't get himself under control, he's very likely to kill you," said Thompson.
The authors have written a new book about van der Sloot called "Portrait of a Monster."
They showed INSIDE EDITION's Les Trent a photo of a blood-soaked shirt van der Sloot allegedly used to smother Flores after he beat her.
Among van der Sloot's possessions when he fled Peru was a biography of mob legend Al Capone.
Lisa Pulitzer says she got a new insight into Natalee Holloway's fate from the violent way that van der Sloot allegedly did away with Flores.
"Originally I thought that perhaps it was an accident—that Natalee died perhaps of an overdose, maybe she had a seizure. But then I started to question whether in fact Joran callously killed her and discarded her the way he did with Stephany," said Pulitzer.