A man and a 25-year-old woman were arguing and fighting with another man, 54-year-old Willie Holmes, near the Central station around 1 p.m., police said.
Police said that's when Holmes took out a knife and stabbed the woman in the back.
Holmes fled the scene on foot, but officers later found him, took him into custody and recovered a weapon.
The victim was taken to Mount Sinai Hospital, where she was pronounced dead.
The Cook County Medical Examiner's Office later identified her as 25-year-old Emily Carlson of Glendale Heights.
Holmes is charged with first-degree murder, police confirmed on Saturday.
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