Arbery, a 25-year-old African American, was fatally shot on Feb. 23 while jogging in Glynn County, Georgia. No arrests were made in the case until a cellphone video appearing to show Arbery being shot and killed was leaked on May 5.
Two days later, father and son Gregory and Travis McMichael were arrested and charged with Arbery's murder.
"We are committed to a complete and transparent review of how the Ahmaud Arbery case was handled from the outset," Carr said in a statement. "The family, the community and the state of Georgia deserve answers, and we will work with others in law enforcement at the state and federal level to find those answers."
The request to the DOJ includes an investigation into the discussions between the offices of Brunswick Judicial Circuit District Attorney Jackie Johnson and Waycross Judicial Circuit District Attorney George E. Barnhill.
Johnson first recused herself from the Arbery investigation over a conflict of interest, saying in a letter that Gregory McMichael, 64, had retired as an investigator with the Brunswick District Attorney's Office and had previously served as a Glynn County police officer.
Barnhill recused himself next. In a letter to the Glynn County Police Department, first reported by the New York Times, he explained that there was not enough probable cause to arrest the McMichaels.
According to Carr's statement, at the time Barnhill accepted the case, neither district attorney revealed to Carr's office that Barnhill had "already taken a role in the case in reviewing evidence and advising the Glynn County Police Department regarding whether to make arrests in the case."
On Sunday, the National District Attorneys Association issued a statement disagreeing with Barnhill's decision to share his opinion of whether the McMichaels should be arrested after he decided to recuse himself from the case.
"In this case, District Attorney Barnhill determined he had a conflict in pursuing the investigation into Mr. Arbery's death. At that point, his involvement should have ceased. Instead, District Attorney Barnhill wrote a letter, which has now become public, in which he offered a gratuitous and detailed opinion regarding the hurdles to any prosecution of the individuals involved in the shooting of Mr. Arbery," the statement said.