A federal grand jury on Monday indicted one of two men accused in the slaying of the student body president at the University of North Carolina at Chapel Hill, adding on to state murder charges.

Demario Atwater, 22, was indicted on one count of carjacking resulting in death, and carrying and using firearms during and in relation to carjacking, both of which could allow federal authorities to seek a death sentence.

State prosecutors had already charged both Atwater and Laurence Lovette, 17, with murder in the March 5 death of Eve Carson, 22, of Athens, Ga. Her body was found early that morning in the middle of a residential street near the school's campus. She had been shot five times, including once in the head with a 12-gauge shotgun.

• Click for photos of Eve Carson

• Click for photos of the suspects

"It's a matter of prosecutorial decision making," said Lynne Klauer, a spokeswoman for the U.S. Attorney's office in Greensboro. "We have an obligation to bring charges where there has been a federal offense. This is a case where it fits ... federal offenses as well."

Atwater already faces the death penalty if convicted on state murder charges. Lovette can't be sentenced to death in either state or federal court because the crime was committed before he turned 18.

U.S. Attorney General Michael Mukasey must approve seeking a death sentence in the federal case. Prosecutors said Monday he has yet to do so. The federal indictment also charges Atwater with being a felon in possession of firearms and possessing a short-barreled shotgun that had not been properly registered to him.

Federal executions are rare. Only three people, including Oklahoma City bomber Timothy McVeigh, have been put to death by the federal government since it resumed executions in 2001 after a 38-year hiatus. Executions are even more rare in Orange County, which hasn't returned a death sentence in about 70 years.

But Dr. Lawson Bernstein, a clinical and forensic psychiatrist who has testified as an expert witness in both state and federal death penalty cases, said federal authorities have begun stacking charges that could lead to a death sentence in more than one venue to boost the chances of winning a guilty verdict.

"This is just the state of the prosecution in these types of cases where there's a particularly heinous crime," he said.

Authorities believe Atwater and Lovette kidnapped Carson from outside her Chapel Hill home just before 4 a.m., stole her sport utility vehicle and took her to several ATMs, eventually withdrawing $1,400.

Both suspects were arrested separately a week later after authorities released surveillance photos, including one that showed a man reaching toward an ATM from what appears to be Carson's Toyota Highlander.

Messages left with attorneys for Atwater and Lovette were not returned on Monday.

News of Carson's death led to an immediate outpouring of grief on the North Carolina campus, with thousands gathering for an impromptu memorial service. A massive crowd also attended funeral services for Carson in her hometown of Athens, where she had been student body president at her high school.

Orange and Chatham County District Attorney Jim Woodall said Monday that his office had been in communication with the U.S. Attorney's office regarding possible charges against Atwater, and that their case against him shouldn't affect the prosecution on state charges.

After his arrest in Carson's death, authorities charged Lovette in the death of Duke University graduate student Abhijit Mahato. Mahato was found dead Jan. 18 in his apartment near the university's campus in Durham, about a 20-minute drive from Chapel Hill.

Stephen Oates, 19, of Durham, also is charged with murder in Mahato's death. An autopsy report found that Mahato was shot once in the forehead.