According to a spokesmen, the three people were taken into custody earlier Wednesday. No charges have yet been filed.
WATCH: CPD give update on South Chicago shooting
CPD give update on South Chicago shooting
The shooting happened around 7 p.m. Sunday in the 8600-block of South Kingston Avenue.
David DeVeaux Jr., 20, and Jason Mundo, 18, were killed in the shooting. Two of their friends were injured. Police said at least two shooters, armed with a rifle and two handguns, walked up and opened fire.
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Detectives said at least three different types of shell casings were found at the scene.
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South Chicago Pastor Tom Kennington said all four victims worked for him at a church thrift store.
A motive for the shooting remains unclear. Police and DeVeaux's family asked anyone with information to come forward.