Sixteen-year-old Andres Yanez borrowed his older brother's SUV on Thursday evening and went out with several friends.
When they were south of Midway airport, police and family members say a second vehicle approached them.
"Some car pulled in and they started throwing gang signs at us and they started ramming them. So my brother got scared and started taking off and they were just chasing him and hitting him," said Francisco Yanez, victim's brother.
Yanez and his friends in the SUV had been rammed repeatedly from behind as they headed north on Cicero. The 16-year-old lost control. The SUV flipped over into the oncoming lane. Yanez - who was not belted in - was thrown from the vehicle and killed. A second car then collided with the SUV alongside the sound barrier wall at Midway Airport.
The driver of the vehicle who was doing the ramming didn't stop. Police believe it to be a van, and are believed to be examining images from cameras along Cicero that might have captured the vehicle on tape.
Seconds before the fatal crash, the van police are looking for clipped a westbound car at the busy intersection of 63rd and Cicero, and there is a camera on the northwest corner of that intersection.
Yanez is the third of four children. His family hopes that witnesses will come forward to help police.
"I hope they catch themguys. It's not fair to take innocent lives," said Francisco Yanez.
Police have released a general description of the vehicle they're looking for. They say it's a black Chevy van with gold trim but no specifics beyond that.
Searching video feeds from cameras along Cicero takes time. It's unclear if police have an image that will be helpful to their investigation.
Officials are talking to the young men who were in the SUV with Yanez.