Police found the victims inside a second floor apartment in south suburban Harvey late Sunday night. Three suspects were later taken into custody.
Friday afternoon, a fourth person turned themselves in to police.
Twenty-year-old Donysha Stovall, her 9-year-old daughter Clarisma Torrey and 16-year-old Shaquille Davis were killed. Stovall's 4-year old son survived the shooting.
No charges have been filed.