The crash happened around 9:42 p.m. on the southbound lanes of I-55 near Blodgett Road in the Channahon area.
Illinois State Trooper Clay Carns, 35, was removing debris from the highway when he was struck by a Chevrolet Silverado pickup truck, ISP said.
Trooper Carns was rushed to a hospital in Joliet where he died from his injuries.
"It's Christmas Eve...so, this hurts in a very particular way," Illinois State Police Director Brendan F. Kelly said.
The driver of the Chevrolet was identified as John Fleet of Wilmington. He remained at the scene, state police said, and now faces a Scott's Law charge and multiple Illinois Vehicle Code citations by the Will County State's Attorney's Office.
The charges against Fleet are not detainable offenses, and so he has since been released, ISP said.
Carns served 11 years with Illinois State Police. He is survived by his wife, two children, siblings and his parents.
"Please remember that when you're in your home peacefully, safely, enjoying your family tonight and tomorrow morning Christmas Day, that's not a coincidence. That's not some kind of Christmas miracle. It's possible because a police officer made it possible," Kelly said.
The Illinois Fraternal Order of Police released a statement, saying, "As you hug your loved ones this holiday, think how fortunate you are that there are public servants like Trooper Carns, dedicated and selfless law enforcement officers who put their lives on the line every day to keep all of us safe. Clay's wife, children and parents will no longer be able to hug him on this Christmas Eve simply because Clay was doing his job in a dangerous profession that many citizens take for granted. Please take a moment today to remember and appreciate Trooper Carns' life and sacrifice, pray for his loved ones, and be thankful that we still have men and women who face danger 24 hours a day so we can embrace our own family and friends during the holidays."
The deadly crash happened as the state observed Scott's Law Day. It's also known as the "Move Over" Law, and it requires drivers to slow down or move over for construction or emergency vehicles.
Scott's Law was created when Chicago Fire Lt. Scott Gillen was killed on the Dan Ryan 24 years ago. He was hit and killed by a drunk driver as he helped people who had been in a crash.
On January 1, Scott's Law will be slightly changed.
It will require people to both slow down and move over, if traffic allows, for emergency or construction vehicles that are stopped on the side of a road.
The law currently gives drivers an option of either slowing down or moving over.
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