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At least four people were wounded by gunfire overnight at a gathering on the Far South Side in the Riverdale neighborhood, Chicago police said.

Shortly after 3:15 a.m. Thursday, a group was outside in the 600 block of East 133rd Street when someone opened fire, striking four victims, police said.

A 21-year-old man suffered wounds to the arm and thigh and was taken in critical condition to University of Chicago Medical Center. A 31-year-old man suffered wounds throughout his body and was taken in critical condition to Advocate Christ Medical Center in Oak Lawn. Another victim, 29, was shot in an arm, and got herself to Christ Medical Center where her condition was stabilized.

A fourth victim suffered a wound to the shoulder and got himself to Roseland Community Hospital but he was transferred to U. of C. Medical where his condition was stabilized.

No one was in custody and detectives were investigating.