Birmingham, Alabama – The prime suspect in the infamous 2005 disappearance of American student Natalee Holloway has newly confessed to her murder, prosecutors and the victim's family said Wednesday. And shocking details of the gruesome killing have reportedly come to light.

As part of a guilty plea entered in a related case, Joran van der Sloot (36) confessed to killing Natalee Holloway on the Caribbean island of Aruba where she was vacationing.

Holloway (18) disappeared while on a high school graduation trip to Aruba. Her body has never been found, and the mystery surrounding her disappearance captivated the nation.

Van der Sloot pleaded guilty during a court hearing in Birmingham, Alabama, on Wednesday over attempting to extort money from Holloway's mother in 2010 in exchange for information about her daughter's disappearance.

While he cannot be charged with Natalee's murder due to Aruba's 12-year statute of limitations, van der Sloot pleaded guilty and was sentenced to 20 years for wire fraud and extortion. The length of his sentence was given in exchange for "full, complete, accurate, and truthful information regarding Natalee Holloway’s disappearance," as per to the US Department of Justice.

"Today marks the end of 18 years of wondering what happened to Natalee Holloway," US District Attorney Prim Escalona said following the hearing. "Natalee can rest knowing that justice was served."

Natalee's mother, Beth Holloway, also spoke to reporters outside the court, saying, "Today, I can tell you with certainty that after 18 years, Natalee's case is solved... as far as I'm concerned, it's over."

"Joran van der Sloot is no longer the suspect in my daughter’s murder," she said. "He is the killer."

Van der Sloot was extradited to the United States in June from Peru, where he is serving a 28-year prison sentence for the 2010 murder of Stephany Flores, a 21-year-old Peruvian woman.

Under an agreement with the Peruvian authorities, van der Sloot is to be returned to Peru following the US extortion case to serve the remainder of his sentence there for the murder of Flores.

In legal documents obtained by TMZ, van der Sloot admitted to killing Holloway because she refused his sexual advances on the beach after a night out at a local bar.

"I start feeling her up again and she tells me no," van der Sloot said. "She tells me she doesn't want me to – to feel her up. Uh, I insist. I keep feeling her up either way."

When Natalee knee-ed her assailant in the crotch in self-defense, the man confessed to kicking her "extremely hard" in the face, the force of which he said knocked her out. Afterward, van der Sloot said he grabbed a nearby cinder block and "[smashed] her head in with it completely."

He then allegedly carried her body into the ocean and pushed her out to be carried away by the surf.

Shockingly, the alleged murderer offered up a brazen apology to the family after his confession, claiming he had found religion.