Chauncey Lee Daniels is facing numerous charges, including murder and three counts of aggravated assaulted, after authorities said he shot four people and then exited a MARTA train at the West Lake station around 4:30 p.m.
Police said the shooting of the man appears to be a "targeted, isolated incident".
The Metropolitan Atlanta Rapid Transit Authority, the metro's governing body, said the suspect has been arrested and investigation is underway.
She says MARTA officers caught the suspect at the West Lake station.
The other victims are said to be in stable condition with non-life-threatening injuries at Grady Memorial Hospital. Buses returned to their normal operating schedule about 9:20 p.m.
"He worked with him and they had altercations", said one woman who said her sister was dating the victim. At least four people were reportedly shot, and the station has been closed while law enforcement secures and investigates the scene.
The suspect is in custody, but his name has not been released.
You can expect delays on the eastbound line as a result of the incident, but MARTA established shuttles to carry passengers from H.E. Holmes station to Ashby Station during the closure.
"We have increased our presence throughout the entire MARTA system and will continue to remain vigilant in protecting all of our riders".