Authorities were investigating Monday after a driver was killed in a shooting following a police pursuit along Interstate 88 in DeKalb County, Illinois State Police said.

The shooting was reported at around 3:12 p.m. on the westbound lanes of the Ronald Reagan Memorial Tollway near Keslinger Road. State police said a Naperville police officer initially located a vehicle wanted in connection with a missing person who was reportedly experiencing a mental health crisis.

The driver reportedly displayed a gun then drove away.

Warrenville police later found the vehicle and pursued the driver, who again displayed a gun. As the vehicle entered DeKalb County, the vehicle struck spike strips and came to a stop. According to state police, Warrenville police and the driver reportedly fired shots during the incident. The driver sustained a gunshot wound.

The driver was taken to an area hospital, where he was pronounced dead.

It wasn’t immediately clear who fired the shots that killed the individual.

A portion of the tollway was closed while police conducted an investigation but reopened later Monday.

The ISP Division of Criminal Investigation is investigating the Warrenville officer’s use of force. ​