Police Maj. Keith Meadows said the rapper, whose real name is Mario Hamilton, was fatally shot in the chest after getting into an argument with another individual.
He was transported to Grady Memorial Hospital where he was pronounced dead.
Meadows told The Associated Press late Friday that police have not been able to identify the shooter. He said investigators have been interviewing those who were inside the studio. He said as many as 20 people were inside the small office-type building at the time of the shooting, which took place around 5:30 p.m., but they were in different places.
Police have not recovered the handgun that was used. Investigators remained at the scene late Friday evening.
"Right now we're just trying to....identify who may have seen what, really just trying to put the pieces of the puzzle together," Meadows said. "It seems everybody witnessed something very different. We're just trying to go back and make sense of everything."
Slim Dunkin had appeared on a number of songs with the rapper Waka Flocka Flame. The website Mtv.com reported that the Brick Squad Monopoly rapper was on a solo track and had recently released a 20-track mix tape that featured Gucci Mane, Roscoe Dash and Pastor Troy.
"It appears the victim was scheduled to do a photo shoot," Meadows said of Friday's events. "Before the video shoot took place, it appears the victim and suspect got involved in a verbal altercation. We don't know what that altercation was about."
"The suspect produced a weapon, discharged that handgun one time, striking the victim in the chest," Meadows said.
Meadows said the victim was in his early 20s and resided in the Atlanta area.
Many fans were posting messages late Friday night on a Facebook page for the rapper.
The website AllHipHop.com last February described Slim Dunkin, a Detroit native, as an up-and-coming talent with "a unique lyrical ability and style all his own."
In an interview with the website, he described himself as someone "trying to provide for his family by making something out of nothing just trying to beat the odds."
"I don't have amazing lyrical ability I just know how to speak on what I been through and where I came from," he said.
Asked what to expect from him in 2011, he responded: "Music, music, music!"