The boys were biking north on Roy Avenue, approaching Lyndale Avenue, just after 8:20 p.m., when a vehicle traveling west quickly on Lyndale drove through a stop sign and hit the teens in the intersection, police said.
The children were taken to Loyola Hospital with serious injuries. One was critically hurt.
The other has been released from the hospital.
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Video shows the white sedan involved in the crash driving away after the incident, police said.
Investigators said they found the vehicle with front-end damage in Elmhurst, and have obtained search warrants. They also took the car's owner into custody, but police say that person is not cooperating.
It might be days before charges are filed.