Originally Published: 18 OCT 23 05:46 ET

Updated: 18 OCT 23 13:57 ET

By Holly Yan, Devon M. Sayers and Aaron Cooper, CNN

Birmingham, Alabama (CNN) — Almost two decades after Natalee Holloway vanished in Aruba, the man long suspected of killing the Alabama teen has confessed to her killing, according to a court filing.

“It’s over. Joran van der Sloot is no longer the suspect in my daughter’s murder. He is the killer,”Holloway’s mother, Beth Holloway, said Wednesday.

“He gave a proffer in which he finally confessed to killing Natalee,” Holloway said. “After 18 years, Natalie’s case is solved.”

In a proffer, a defendant offers information they know about a crime, often as part of a plea deal.

Van der Sloot, 36, pleaded guilty in federal court Wednesday to extorting and defrauding the Holloway family. He was accused of trying to sell information about the location of Holloway’s remains to her family in exchange for $250,000.

Holloway’s body has never been found. In 2012, an Alabama judge signed an order declaring her legally dead.

But on Wednesday, a federal judge who reviewed van der Sloot’s proffer said there’s a reason why Natalee Holloway’s body would never be found – though she did not elaborate.

But the deaths of Holloway and a Peruvian woman who van der Sloot previously admitted to killing prompted Judge Anna Manasco to sentence van der Sloot to 20 years on the federal charges.

“I have considered your confession to the brutal murder of Natalee Holloway,” the judge said after reading van der Sloot’s proffer.

“You have brutally murdered in separate incidents years apart two beautiful women who refused your sexual advances.”

Van der Sloot had been arrested multiple times in connection with Holloway’s death. He was subsequently released by Aruban authorities who cited a lack of direct evidence.

Van der Sloot is serving a 28-year prison sentence in Peru for the 2010 murder of Stephany Flores. Peruvian officials allowed his temporary release to the US in June to face the extortion and wire fraud charges.

Van der Sloot will return to Peru to finish his murder sentence in the Flores case. Afterward, he will return to the US to start his prison sentence for the federal extortion and wire fraud charges.

18 years of mystery and misery

Holloway was visiting Aruba on a high school graduation trip when she vanished in 2005.

The 18-year-old was last seen leaving a nightclub with van der Sloot and two other men, brothers Deepak and Satish Kalpoe.

The three men were arrested in 2005 but were released due to insufficient evidence.

They were rearrested and charged in 2007 for “involvement in the voluntary manslaughter of Natalee Holloway or causing serious bodily harm to Natalee Holloway, resulting in her death,” Aruban prosecutors said at the time.

But a few weeks later, an Aruban judge ordered van der Sloot’s release, citing a lack of direct evidence that Holloway died from a violent crime or that van der Sloot was involved in such a crime. The Kalpoe brothers were also released.

Why van der Sloot was charged in the US

While US officials don’t have jurisdiction over the criminal investigation in Aruba, a federal grand jury in Alabama indicted van der Sloot for an alleged plot to sell information about Holloway’s remains to her family.

According to the indictment, van der Sloot’s scheme took place between March and May 2010.

He was indicted in June 2010 on charges of extortion and wire fraud.

In the weeks between the alleged extortion and indictment, van der Sloot killed 21-year-old Flores in his hotel room in Peru on May 30, 2010.