The shooting happened around 10 p.m. Monday in the northbound lanes of I-57 near Cicero Avenue in Oak Forest.
The 55-year-old woman was on her way to work when someone fired three shots at her vehicle. She was pronounced dead at the scene.
The victim worked for the U.S. Postal Service for 25 years.
The USPS and the family members identify the victim as Tamara Clayton-Shelton.
It is unknown if she was the intended target.