Georgia's attorney general asked the U.S. Justice Department on Sunday to investigate how local authorities handled the killing of Ahmaud Arbery.
Attorney General Chris Carr said in a statement that local prosecutors had not informed his office that they had advised police on whether Gregory McMichael, 64, and Travis McMichael, 34, should be arrested after Arbery was killed Feb. 23 in Brunswick.
Arbery, 25, who was black, was shot to death after being chased by white men in a pickup truck. Arbery was unarmed and on a jog at the time of his death, his family says.
The Georgia Bureau of Investigation took the McMichaels, who are father and son, into custody Thursday after the release of a video showing Arbery's killing sparked nationwide protests. The men face charges of felony murder and aggravated assault.
On Sunday, the GBI said a man was arrested after investigators saw a Facebook post that threatened future protests. Rashawn Smith, 20, was booked on suspicion of disseminating information related to a terroristic act, the agency said.
Additional information about the allegation wasn't immediately available.
Carr's office said the Brunswick Circuit District Attorney's Office, where Gregory McMichael had worked as an investigator, asked the attorney general on Feb. 27 to appoint a different prosecutor.
Carr handed the case off to the Waycross Circuit District Attorney George Barnhill on the same day, although prosecutors in neither office told the attorney general that the government's newly appointed lawyers had already reviewed evidence in Arbery's killing, Carr's office said.
On April 2, Barnhill confirmed an "initial opinion" of Arbery's case made the day after his death, the attorney general said. The district attorney recommended that no arrests be made.
Carr said his office will turn over its file on prosecutorial appointments to the federal government.
District Attorney Jackie Johnson of the Brunswick Judicial District has said no prosecutors in her office told police not to arrest the McMichaels.
In a statement Sunday, lawyers for Arbery's mother called prosecutors' handling of the case a "potential cover-up" and said they hoped the Justice Department would conduct a comprehensive investigation.
"There are far too many questions about how this case was handled and why it took 74 days for two of the killers to be arrested and charged in Mr. Arbery's death," they said.
The attorney general's announcement comes a day after the GBI said it is reviewing surveillance video that appears to show Arbery entering a construction site just before he was killed.
Video from the day of Arbery's death, obtained by The Atlanta Journal-Constitution, shows a person matching Arbery's description walking up to a house under construction, entering and then leaving shortly later.
"We are indeed reviewing additional video footage and photographs as part of the active case," the GBI said in a statement. "It is important to note that this footage was reviewed at the beginning of the GBI investigation and before the arrests of Gregory and Travis McMichael."
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A statement from attorneys representing Arbery's family say the new video "is consistent with the evidence already known to us."
"Ahmaud's actions at this empty home under construction were in no way a felony under Georgia law. This video confirms that Mr. Arbery's murder was not justified and the actions of the men who pursued him and ambushed him were unjustified," the family's lawyers said in a statement.
Gregory McMichael saw Arbery in February on foot running down a street in Brunswick, a coastal city between Savannah, Georgia, and Jacksonville, Florida, according to a police report. He grabbed his gun and, with his son, who was also armed, jumped into their pickup truck to chase Arbery. The McMichaels claim that they thought Arbery was a burglar and that they armed themselves because they thought he might have a gun, authorities said. Representatives for Arbery's family deny that he was armed.
In video of the shooting, Arbery is seen running down a road as a white pickup truck is stopped in front of him. He runs around the vehicle, and a shot is fired. The video then shows Arbery and another man appearing to tussle as two more shots are fired. Travis McMichael shot and killed Arbery after the confrontation, authorities said.
NBC News does not know what occurred before the events shown in the video.
Barnhill, one of the prosecutors who first handled the case, defended the actions of the McMichaels and their neighbor in the truck. In a letter to the Glynn County Police Department obtained by NBC News, Barnhill wrote that the men had "solid first hand probable cause" to chase Arbery, a "burglary suspect," and stop him.
Barnhill also said he believed Travis McMichael "was allowed to use deadly force to protect himself" under Georgia law.
Lawyers for Arbery's family say Arbery was a victim of "racial violence," and the Rev. James Woodall, state president of the Georgia NAACP, called his death a "modern-day lynching."
The shooting has sparked nationwide outrage and protests, and on Friday people across the country ran laps to honor Arbery. His mother, Wanda Cooper-Jones, told NBC News, "I wish the world would have gotten the chance to know Ahmaud, to really, truly love Ahmaud."