A longtime postal worker was shot and killed along an interstate in a suburb of Chicago -- just a few miles from where another shooting wounded three people only hours before, police said.

The Postal Service said Tamara Clayton-Shelton had been employed with the agency since 1993 and was a mail handler at the Chicago International Military Service Center facility.

State police said Clayton-Shelton, 55, was alone in a car when she was shot around 10 p.m. Monday on northbound Interstate 57 near Oak Forest, just south of Chicago. She was pronounced dead at the scene.

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Police who responded to the scene initially believed it to be a single-vehicle crash before finding Clayton-Shelton with an apparent gunshot wound.

The Postal Service said in a statement it was “deeply saddened on hearing of this tragedy” and offered its prayers to Clayton-Shelton's family.

The shooting occurred about six hours after a 38-year-old man was critically wounded in a shooting a few miles away on I-57 near Calumet Park. Police said 15- and 12-year-old boys were also shot and wounded in that incident. Both are in stable condition.

An 8-year-old girl in the same vehicle wasn’t shot but was also taken to a hospital.

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A police spokesman on Tuesday declined to say whether investigators believe the shootings are linked, saying officers “have come to no conclusions.”

Additional information was not immediately available.

The Associated Press contributed to this report.