Calvan Colbert, 18, of the 5200-block of South Indiana Avenue, was charged Monday with three counts of first-degree murder and two felony counts of aggravated battery causing great bodily harm.
In October, Anthony Jackson and Lawrence Brown were each charged with several felonies, including first-degree murder.
Police said the men allegedly opened fire on a crowd just after midnight on Sept. 29 in the 300-block of West 42nd Street, near a playground.
Ayanna Northern, 22, was fatally shot in the chest. Antian Hardmon, 25, and Tyrone Spikes, 28, were both fatally shot in the head.
A 24-year-old woman was shot in the leg and transported to Stroger Hospital, where her condition stabilized. Police said a man in his 20s walked into Provident Hospital with a gunshot wound to the leg. Both of their injuries were not life-threatening.
Colbert is due in bond court Monday.