Prosecutors have dismissed murder charges against a man accused in the death of Chandra Levy, a Washington, D.C., intern whose 2001 disappearance created national headlines.

Federal prosecutors said they can no longer prove a case against Ingmar Guandique because of “recent unforeseen developments that were investigated over the past week,” Bill Miller, public information officer for the U.S. Attorney’s Office in Washington, said in a news release.

He did not specify what the developments were.

Guandique was sentenced to 60 years in prison after being convicted in 2010 of killing and robbing Levy.

Guandique’s lawyers appealed the conviction and questioned the credibility of prosecution witness Armando Morales, a convicted felon and former gang member who testified that Guandique confessed to him that he killed Levy.

A judge granted a new trial in May 2015. Miller said prosecutors will not pursue the retrial.

Levy, a 24-year-old California native, was in Washington working as an intern for the Bureau of Prisons when she was last seen on May 1, 2001. Her skull was found over a year later, on May 22, 2002, in Washington’s Rock Creek Park.

Levy’s disappearance gained national attention after her parents discovered a connection with Gary Condit, who was then a congressman for Levy’s California district.

Condit was never a suspect in the case, but he and Levy were romantically linked and Condit was questioned intensively about Levy’s whereabouts.

Police arrested Guandique in February 2009.

He was then serving a 10-year sentence for attacking two other women in the park.

Miller said that Guandique will be released to the custody of U.S. Immigration and Customs Enforcement, where he faces deportation proceedings.