Police Superintendent Garry McCarthy said all four are charged with attempted murder and aggravated battery in Thursday's attack in Cornell Square Park on the southwest side.
Investigators believe Tabari Young, 22, was the principal gunman and he was charged Tuesday, McCarthy said. Bryon Champ, 21, who was charged a day earlier, was also a shooter, the police superintendent said.
A suspected lookout, Brad Jett, 22, and Kewane Gatewood, 20, have also been charged, McCarthy said.
Among those injured in the shooting were two teenagers and 3-year-old Deonta Howard, who is recovering from surgery after being shot near his ear.
Authorities describe Champ as a documented gang member. He was convicted in July 2012 on charges of unlawful use of a weapon by a felon and sentenced to Cook County Jail's boot camp.
Police had recorded 306 murders and 1,402 shooting incidents this year in Chicago as of Sept. 15, down 20 and 22 percent, respectively, from the same period in 2012. Police say overall violent crime is down about 15 percent, according to new figures released Monday.