Speaking publicly for the first time since Natalee Holloway's disappearance 12 years ago, a classmate on the trip to Aruba said she is certain she saw Joran van der Sloot the last night Holloway was ever seen. Van der Sloot, who is behind bars for a separate crime, remained the primary suspect in Holloway's disappearance, though he was never formally charged.

Holloway, who was 18 at the time of her disappearance, was last seen leaving a popular bar called Carlos 'n Charlie's. Jessica Caoila, a friend of Holloway's, said in an interview during the premiere of a new Oxygen series called "The Disappearance of Natalee Holloway" this weekend that she is positive she saw Van der Sloot that night.

"What I can tell you is he was there multiple nights of our trip," she said. "I believe it was the second to last night I saw him at the casino. He was absolutely at Carlos 'n Charlie's. One thousand percent."

Van der Sloot was a constant presence during their trip, Caiola remembered.

"I remember seeing Joran van der Sloot at the casino at our hotel," she said. "That was the first time I saw him and I remember chatter of him: 'He's so cute,' 'Who's going to hook up with him?' Those sorts of things were floating around. That was probably the extent to which I got close to him."

natalee-ann-holloway Joran van der Sloot remains the primary suspect in Natalee Holloway's disappearance. Photo: FBI

Caoila recalled seeing Holloway get inside a car outside the bar that last night. Authorities later said Van der Sloot and two Surinamese brothers were inside the car. All three were arrested and questioned in connection with her disappearance but were ultimately released for a lack of evidence.

"While we were waiting for street food, I remember seeing Natalee in a white car driving away," Caoila said. "The window was down so we could see it was her in the back of the car. My impression was, 'Oh, great, she found a ride back to the hotel."

When Holloway didn't show up to meet her classmates to depart for the United States the next morning, many of her friends assumed she'd overslept. It was only when they couldn't get in touch with her that they became concerned. Caiola said she now believes van der Sloot killed Holloway, but she thinks it happened after she was reported missing.

"I thought she was still alive and she had been sold or traded, something of that nature and we could find her," she said. "The reason I thought this is there was no tinge of her clothing."

Van der Sloot was arrested five years after Holloway vanished for the murder of a 21-year-old student named Stephany Flores in Peru. Flores reportedly stumbled upon files relating to Holloway on Van der Sloot's computer when he killed her.

Holloway herself was officially declared dead in 2012, though her body was never found. Van der Sloot remains the primary suspect in Holloway's death, and her father, Dave Holloway, has continued to search for evidence of what happened to his daughter. He announced Wednesday that a joint search with a private investigator led him to what he believes are human remains at an undisclosed location in Aruba. The remains have been sent for DNA testing to confirm if they belong to Holloway.

Natalee Holloway went missing 12 years ago, but her father thinks he may have found a credible new lead.