The FBI will join Illinois State Police in investigating a police shooting in suburban Chicago that killed a Black man who was a passenger in a vehicle and wounded the Black female driver, a prosecutor announced Friday.

Lake County State's Attorney Michael Nerheim said he asked the U.S. Justice Department to review the circumstances surrounding the fatal shooting of Marcellis Stinnette, 19, and the wounding of his girlfriend, Tafara Williams, this week in Waukegan.

“I am confident in the work being done by the Illinois State Police and welcome the assistance of the FBI,” Nerheim said in a statement. ”As I have said before, once the investigation is concluded, all the evidence will be reviewed and a final decision will be made with respect to any potential charges.”

Waukegan police have said the pair were in a vehicle that fled a traffic stop late Tuesday and that the vehicle was later spotted by another officer. Police said that as the second officer approached, the vehicle started moving in reverse and the officer opened fire. No weapon was found in the vehicle.

The officer who shot the couple is Hispanic and a five-year veteran of the Waukegan Police Department. The officer who conducted the original traffic stop is white, police said.

During a Thursday demonstration, Clyde McLemore, head of the Lake County chapter of Black Lives Matter, called for a federal investigation. Activists and relatives of the couple also have demanded the release of police video of the shooting, which authorities say has been turned over to investigators.

Activist Chris Blanks said the video is particularly important because the police version of events and the version Clifftina Johnson said her wounded daughter, Williams, shared with her appear to contradict each other.

Johnson said her daughter told her that Williams and her boyfriend had done nothing to provoke the officer.

Nerheim urged calm while the investigation takes place and pledged transparency.