Chicago police said the girl was in a car with family members in the 2300-block of West 72nd Street shortly before 8 p.m. when someone began firing shots down the street.
The girl was struck in the back of her head. Her family immediately drove her to Comer Children's Hospital, where she is listed in grave condition, according to Chicago police.
"I was in my kitchen cooking, and all I heard were gunshots," said neighbor Diana Velasco. "Probably six I believe? And it's usually a very calm neighborhood so I didn't expect that at all."
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Community activist Andrew Holmes said the girl was out celebrating her 12th birthday with her family when she was shot. Now those family members are at her bedside.
No further injuries were reported. No one is currently in custody. An investigation by Area 1 detectives is ongoing.
So far in 2022, 41 children have been shot and 12 of them have been killed, an increase of 17% compared to 2021.
Chicago Police Superintendent David Brown said there will be a price to pay for whoever pulled the trigger.
"The Chicago Police Department will bring the full force of the department to solve this crime. This was heinous, reckless, senseless and the gangs involved, you know who you are, we're coming after you," he said.
The area where the shooting occurred has seen an increase in violence and shootings of about 30%.
Crime is up overall in the area by 54%.