Brooks was reported to police for sleeping in a car blocking the drive-thru lane of the fast-food restaurant. He was shot and killed in a late-night struggle with Atlanta officers after he failed a field sobriety test and resisted arrest, Georgia authorities said on Saturday.

Video circulating online appears to show Brooks running from officers as a Taser was deployed, before he was shot.

The shooting occurred at a time of heightened tension over police brutality and racial tension with calls for reforms across the US following the May 25 death of George Floyd in Minneapolis. Atlanta was among US cities where large crowds of protesters took to the streets.

"What has become abundantly clear over the last couple of weeks in Atlanta is that while we have a police force full of men and women who work alongside our communities with honor, respect and dignity, there has been a disconnect with what our expectations are and should be, as it relates to interactions with our officers and the communities in which they are entrusted to protect," mayor Bottoms said at her news conference.

A crowd of demonstrators gathered on Saturday outside the Atlanta restaurant where Brooks was shot. Gerald Griggs, an attorney and a vice president of Atlanta's National Association for the Advancement of Coloured People chapter, estimated there were 150 people protesting at the scene as he walked with them on Saturday afternoon.

"The people are upset," Griggs said. "They want to know why their dear brother Rayshard Brooks was shot and killed when he was merely asleep on the passenger side and not doing anything."

Even though Brooks struggled with officers, Griggs said, "they could have used non-lethal force to take him down."

The GBI said its agents were reviewing video taken by witnesses, and tweeted that it was aware of and reviewing the video posted on social media.

The agency also posted to Twitter a plea for witnesses to come forward, saying some at the scene "chose not to be interviewed by GBI agents".

Officers were responding to a complaint of a man in a vehicle parked in the drive-thru who was asleep, causing customers to drive around the vehicle.

After Brooks failed a field sobriety test, the officers attempted to place him into custody, according to the GBI. But he resisted and a struggle ensued, leading the officer to deploy a Taser.

"Ultimately, when the officer used a Taser, it was ineffective for the suspect," Atlanta Deputy Police Chief Timothy Peek told reporters at the scene on Friday night. "It did not stop the aggression of the fight. And so the suspect was able to take the officer's Taser from him."

Peek said a second officer also attempted to use a Taser on the struggling man, "but it didn't work against the suspect as well".

The GBI said it was investigating reports "that the male subject was shot by an officer in the struggle over the Taser".

Brooks was transported to a local hospital where he died after surgery, the statement said. One officer was treated for an injury and discharged from the hospital.

Fulton County district attorney Paul Howard said on Saturday his office had already become involved without waiting for the GBI to finish its investigation.

"My office has already launched an intense, independent investigation of the incident," Howard said in a statement, saying members of his staff "were on scene shortly after the shooting, and we have been in investigative sessions ever since to identify all of the facts and circumstances surrounding this incident".

Stacey Abrams, the Georgia Democrat who gained national prominence running for governor in 2018, tweeted on Saturday of the shooting that "sleeping in a drive-thru must not end in death".

"The killing of #RayshardBrooks in Atlanta last night demands we severely restrict the use of deadly force," Abrams' tweet said. "Yes, investigations must be called for - but so too should accountability."

The officers involved in the shooting were not identified. Once its investigation is complete, the case will be turned over to the Fulton County District Attorney's Office for review.

AP, Washington Post