Officials said the K-9, named Loki, and his handler were conducting a traffic stop on the right shoulder of I-90 near Irene Road at approximately 1:30 a.m. when a white Lincoln limousine struck the rear of the deputy's fully marked squad car.
The force of the impact pushed the squad car into the vehicle the deputy had pulled over.
The deputy was out of the vehicle at the time and only received minor injuries from flying debris. However, K-9 Loki was secured in a kennel inside the vehicle at the time of the accident and was transported to an emergency vet clinic in Rockford where he later passed, according to the post.
The two other drivers were transported to area hospitals with non-life-threatening injuries, Illinois State Police said.
A 53-year-old Crystal Lake man has been cited for driving under the influence and failure to yield to an emergency vehicle (Scotts Law), among other citations, police said.
ISP is investigating the accident.