CHICAGO (CBS) — Elgin police released video of the fatal shooting of a woman by an officer during a standoff on the Jane Addams Tollway earlier this month.

An officer shot and killed 34-year-old DeCynthia Clements on March 12, after she allegedly fled a traffic stop, and then stopped her SUV on the tollway.

The 18 minute video ends with police yelling at Clements to drop a knife, before three shots are fired, fatally wounding her.

The video begins with a police pursuit that is then aborted. The video resumes when officers find her car pulled onto the shoulder. They are seen repeatedly trying to convince Clements to get out of the car.

decynthia clements Elgin Police Release Video Of Fatal Police Shooting

Decynthia Clements (Photo supplied to CBS)

Elgin Police Chief Jeffrey Swoboda planned to release video footage of the incident at 3 p.m. Thursday. Police first showed the video to Clements’ family and their attorneys, who have said they plan to file a lawsuit.

“The video of the fatal shooting of DeCynthia Clements released today by the Elgin Police Department raises questions about the unnecessary use of deadly force by an Elgin Police Officer,” Antonio Romanucci, the Clements’ lawyer, said in a statement Thursday morning. “This situation did not have to escalate to such a degree that cost a young woman her life. As we move forward with this lawsuit, those responsible for DeCynthia’s death must be held accountable.”

Police have not elaborated on what happened to prompt Jensen to shoot Clements, or how the fire in her SUV started.

addams shooting Elgin Police Release Video Of Fatal Police Shooting

Police investigate after an officer-involved shooting on the Jane Addams Tollway in Elgin on March 12, 2018. (Credit: CBS)

Clements was taken to St. Alexius Medical Center in nearby Hoffman Estates, where she was pronounced dead. She leaves behind a 21-year-old son.

Her family has described her as a “loving, caring mom.” They also said she was very small, and not a threat to officers trained in deadly force and equipped with shields and body armor.

Illinois State Police were investigating the shooting.