The station has been temporarily closed, and MARTA has set up a bus between stations to accommodate customers during the closure, the statement says. Detectives are seeking to determine if this was a random or targeted shooting.
It's believed all the victims were in their 30's.
A man who was in the train vehicle told Atlanta's Fox 5 television that a man wearing a hat sat next to another passenger, his head bobbing.
Cedric Peterson told WGCL-TV (http://bit.ly/2pf1Tea) that he regularly rides the train after work and the ride started off normally.
The three people who were injured were taken to a hospital. "It was like he was aiming at me, my sister and her boyfriend". The shooting occurred at about 4:30pm local time on Thursday.
By ridership, MARTA is the eighth-largest rapid transit system in America.
Due to police activity, Blue Line trains will not service Holmes & Wst Lake. Police have since confirmed one of those four died.
A MARTA spokesperson said the shooting happened on a train while it was traveling eastbound.
About two weeks ago, a fire caused a bridge to collapse on I-85 in Atlanta. In the meantime, MARTA ridership is up to some degree as some commuters opt for the train as a way to avoid traffic headaches.
A suspected shooter is in custody in Atlanta after four people were shot at a public transit station Thursday afternoon. A suspect has been detained.