Hillsborough, N.C. — A letter made public Thursday confirms federal authorities have opened an investigation into the March 5 shooting death of the University of North Carolina at Chapel Hill's student body president.

U.S. Attorney Anna Mills Wagoner says in the letter, dated April 23, to Orange County District Attorney Jim Woodall, that investigators opened the investigation nine days after Eve Carson, 22, was found dead several blocks from the UNC campus.

Federal sources told WRAL News earlier this month that investigators are looking at carjacking charges against the two men charged in her death – Demario James Atwater, 22, and Laurence Alvin Lovette Jr., 17.

Both already face state charges of first-degree murder, kidnapping and armed robbery, as well as other charges.

If federal prosecutors bring charges, Woodall said, that would mean a separate prosecution; federal involvement would not affect his state case

"They might have some similar charges, but usually, they are going to have some charges for crimes that, frankly, don't exist at the state level," Woodall said.

A federal carjacking charge can carry a death penalty sentence if prosecutors can prove the carjacking was committed during a homicide.

Possible federal charges are significant because Orange County juries have rarely sent someone to death row. The last defendant executed from Orange County was in 1948.

"I think it's well known," Woodall said. "It's been many years since around 1970 or 1971 since there's been a death verdict returned in Orange County."

Under a U.S. Supreme Court ruling, Lovette cannot be tried on capital murder charges, because he was under the age of 18 at the time he allegedly committed the crime.

A hearing to determine whether Atwater will face the death penalty is scheduled for Aug. 11.

Carson, who was a senior from Athens, Ga., had been shot five times, including once to her head with a shotgun, according to an autopsy report; search warrants suggest both suspects might have shot her.