|Surveillance image of a Chevy Cobalt connected to the attack|
One offender appeared to have a gun and the older victim, 37, put his hands in the air, police said. A gold chain was ripped from his neck during the attack.
Other attackers yanked the 21-year-old out of the car, beat him, and stabbed him three times in the chest.
The younger man is in good condition at Illinois Masonic Medical Center, according to police.
Multiple witnesses reported that occupants of a silver 2007 Chevy Cobalt, seen here in a surveillance image, were involved in the attack.
A Toyota Prius and an unknown model of Chrysler also fled the scene.
Police sources were unable to explain why the two victims were targeted by up to three carloads of "suspected robbers."