The incident happened on Saturday at about 9:19 p.m. in the 9300-block of South Bishop Street in Brainerd.
A 15-year-old boy and a 21-year-old woman were inside a car when a woman they knew approached the victims in a silver sedan, Chicago police said.
After a verbal argument, the offender sprayed pepper spray inside the victims' car, according to police.
READ ALSO | Child killed, 10 others shot in Back of the Yards shooting near Damen
The 21-year-old started driving away. The offender followed them in the silver sedan and started shooting into the vehicle.
The teenage boy was shot in the chest and was sent to the hospital in critical condition.
The 21-year-old woman was shot in the head, and sent to the hospital in critical condition where she later died.
No one is in custody, CPD Area Two Detectives are investigating.
INTERACTIVE SAFETY TRACKER | Track crime and safety in your neighborhood