The 35-year-old and 67-year-old were inside a home in the 13000-block of South Muskegon Avenue in Chicago's Hegewisch neighborhood just after 2:30 a.m., when a known male suspect began stabbing them during an argument, police said.
Both women were taken to University of Chicago Medical Center in serious condition.
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The suspect is in custody, and Area Two detectives are investigating.
Police did not immediately release any additional information about the suspect.
This is a developing story; check back with ABC7 Chicago for updates.
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