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A federal arrest warrant was issued Tuesday for a Salvadoran immigrant already in prison in the murder of Washington, D.C., intern Chandra Levy.

Ingmar Guandique, 27, is in federal prison in California for attacking two female joggers in the Washington park where Levy's remains were found nearly seven years ago. He will be formally charged with first-degree murder in Levy's killing at a later time when he returns to D.C.

Interviews with witnesses claimed Guandique bragged to them about killing and raping women, and in two cases, specifically acknowledged killing Levy. When investigators searched his jail cell, they made another chilling find: a photograph of the young, dark-haired Levy ripped from a magazine.

"We believe Miss Levy was a random victim of Mr. Guandique," U.S. Attorney Jeffrey Taylor said in announcing the arrest. "We believe that Mr. Guandique was responsible for murdering Chandra Levy in May 2001."

Guandique told a female correspondent he was writing letters to in prison that he had killed a young woman in a D.C. park, according to the affidavit.

Taylor said "forensic fingerprint analysis," along with the El Salvador native's alleged confession, led authorities to ultimately charge him in Levy's May 1, 2001 murder.

"Additional evidence came to our attention, people came forward," Taylor said. "In weighing it ... we are confident that it is appropriate to charge Mr. Guandique."

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The warrant is the latest development in an investigation that had gone cold for years after destroying the career of former U.S. Rep. Gary Condit of California, who was having an extramarital affair with Levy.

Investigators in 2002 questioned Guandique in Levy's slaying after he was convicted of attacking the women in Washington's Rock Creek Park, where she used to go jogging. He was not arrested in her disappearance at the time.

Authorities said they hoped Guandique would be brought to Washington sometime in the next two months to face a charge of first-degree murder. He was set to be released from prison on Oct. 5, 2011.

If convicted in Levy's death, Guandique could face up to 60 years behind bars.

Levy was 24 and had just completed an internship with the U.S. Bureau of Prisons when she vanished in May 2001 after leaving her Washington apartment.

The Modesto, Calif., woman was wearing jogging clothes when she vanished, and a man walking his dog found her skull and bones in the park a year later.

Chief Cathy Lanier of Washington D.C.'s Metropolitan Police Department said she decided to reopen the Levy case and that of another missing woman — and the renewed effort paid off. Ultimately, both cases have been solved, Lanier said.

"It dawned on me that there's very little I can do or anyone else can do for the Levys other than to offer them justice," Lanier said at a news conference. "This has been a long time coming."

Authorities questioned Condit, Levy's congressman, in her disappearance, but he was never a formal suspect in her death. Levy had confided in friends and family that she and Condit had a romantic relationship.

Condit, a popular Democrat who served in his California district for 12 years, later admitted the affair. The negative publicity surrounding the case was cited as the main reason for his overwhelming primary loss in 2002.

The arrest had been expected since Feb. 20, when Levy's parents Robert and Susan said Lanier had told them it was imminent.

They did not respond to phone messages Tuesday morning, and their spokeswoman Judy Smith declined comment. No one answered the door at the Levys' tan, split-level home in Modesto, Calif.

Authorities defended the delay in a formal arrest and charges in the eight-year-old case. Taylor said it was "appropriate" for police to first focus on those close to Levy, including Condit, and adding that the investigation "took a turn" when her body was found a year after she disappeared.

"Detectives have traveled all over the country doing investigative work," said Lanier.

Investigators spent last week interviewing two inmates Guandique spoke to while in prison, according to a person close to the Levy investigation who spoke on condition of anonymity because he was not authorized to comment on the investigation.

D.C. Mayor Adrian Fenty extended his condolences to the Levy family in announcing the arrest.

FOXNews.com's Catherine Donaldson-Evans and The Associated Press contributed to this report.