He and 17-year-old Laurence Lovette Junior are charged in the case.
Two weeks ago, officials announced the pair is not facing federal charges. But, according to a letter made public July 24, the case has the attention of the U.S. Attorney Office in Greensboro.
The document was sealed under a judge's order after a court hearing in April. It urged the court to delay the release of search warrants related to Carson's shooting death.
The letter does not specify what charges --if any-- federal prosecutors could pursue against Lovette and Atwater.
Investigators believe Carson was taken near her Chapel Hill home on the morning of March 5. Federal law allows for criminal charges punishable by the death penalty, if a car jacking results in a fatality.
An autopsy report that was previously sealed under a judge's order revealed the student body president was shot five times. Lovette and are facing several charges, including first degree murder, robbery and kidnapping.