HILLSBOROUGH, N.C. — Authorities charged two suspects today with first-degree murder in the killing of the University of North Carolina’s student body president.

Demario James Atwater, 21, of Durham, was arrested and ordered held without bond. Shackled at the ankle and waist and with a public defender at his side, Mr. Atwater whispered “yes” when asked whether he understood the charge against him. His next court appearance was scheduled for March 24.

Police said they are still searching for a 17-year-old, Lawrence Alvin Lovett Jr.

The Chapel Hill Police Chief, Brian Curran, declined to say which of the suspects shot and killed Carson, a 22-year-old from Athens, Ga., found lying on a street a week ago about a mile from campus.

The biology and political science major had been shot several times, including once in the right temple. Her body was positively identified the next day, leading to an outpouring of grief at North Carolina.

“I hope the arrest can ease the minds of some in the community,” the District Attorney, Jim Woodall, said.

In the day after Carson’s death, police focused their investigation on a suspect pictured in several surveillance photos using her ATM card.

The Board of Trustees at North Carolina offered a $25,000 reward for information leading to an arrest in her death, and police received hundreds of tips after the first two photos were released over the weekend.

Carson was a prestigious Morehead-Cain scholar at North Carolina, where she was remembered by thousands who gathered Thursday at two campus memorial services. Hundreds of mourners filled the First United Methodist Church in Athens on Sunday at a memorial service in her hometown.

The university said today that a third memorial service would be held next week at the campus basketball arena.