ABC7 obtained security camera footage that shows how the shooting went down. The 8-year-old girl is one of 10 people killed in Labor Day weekend violence in Chicago, police said.
The girl and three adults were sitting in a Subaru SUV at the stoplight on Union Avenue at West 47th Street when police said the shooter's black sedan intentionally pulled up behind them, targeting someone inside.
"Our victims' vehicle was parked facing northbound on Union Avenue with the offender's vehicle directly behind it," said Chicago Police Chief of Operations Brian McDermott. "When the light turned green, the offender's vehicle immediately opened fire on the victims' vehicle."
CPD Supt. Brown discusses shooting of girl, 8
The girl and two adults inside the SUV suffered gunshot wounds, police said.
"The victims' vehicle continued northbound on Union and crashed into a tree," McDermott said.
Inside the SUV, 8-year-old Dejore Wilson was shot in the back and killed. According to Legal Help Firm, Wilson has a twin brother.
At a press conference Tuesday morning, CPD Superintendent David Brown expressed condolences to her family.
"Getting notified about another child being a victim of gun violence is one of the most painful experiences, not only as a law enforcement professional, but also as a parent," Superintendent Brown said.
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"I stand here before you saddened and angered that another child has lost their life to senseless gun violence in the city of Chicago," McDermott said.
While witnesses said people nearby tried to save the little girl's life with CPR, police say the gunman made a U-turn and fled soutbound on Union in a black, newer-model Dodge.
Police said several other family members were in the van as well. Detectives believe the shooting was the result of an ongoing gang conflict.
"And it's possible that other people that were in this vehicle were the targets," Chicago Police Chief of Detectives Brendan Deenihan said. "Obviously the 8-year-old was not, but it was, it doesn't appear there was a random act. It appears that people from this vehicle were definitely targeting someone in that car, or someone they thought should have been in that car."
WATCH: Chicago police discuss shooting that killed 8-year-old girl
Street pastor Donavan Price was on the scene Monday night and went to the hospital with the family. Of the six children under the age of 10 who have been shot and killed this summer, Price has been to half of them.
"This is a different world for children, especially children in Chicago," Pastor Price said. "From fear to confusion and it's just unfortunate that the collateral damage of some of these conflicts of some of these ideals, of some of these mindsets is our children."
Police released a photo of the car the suspects were driving. While they have gotten numerous tips, they continue to ask for the public's help.
"We believe in the detective division that people know who committed this offense, and now we need that information," Deenihan said. "We need people to come forward to help solve this crime."
As detectives at Area One continue to work this investigation, the police superintendent reiterated that in cases like this, they are trying to prosecute federally in hopes that stiffer sentences might act as a deterrent.
Anyone with information about the shooting is asked to report it anonymously to police at CPDTip.com.