Decynthia Clements, 34, was shot three times by an Elgin officer; twice in the head and once in the chest, according to the Cook County Medical Examiner.
The medical examiner's office also said Clements had cocaine in her system.
Police said she had a knife as she got out of her burning car on I-90. Police said they negotiated with her for over an hour after unsuccessfully trying to make a traffic stop. During the negotiations, her vehicle caught fire. Police said she was shot after lunging at officers with the knife.
The family is suing the city of Elgin and the officer involved, claiming that the shooting was unjustified. The officer involved in the shooting, identified as Lt. Christian Jensen, remains on administrative leave.
"The footage depicting the fatal shooting of DeCynthia Clements documents a blatant and unnecessary use of deadly force by an Elgin Police Officer," said the family's attorney, Antonio M. Romanucci. "Furthermore, the video shows that this situation did not have to escalate to such a degree that it cost a young woman her life."
An Elgin city spokesperson declined comment Wednesday morning because they had not seen the lawsuit, but said: "The city understands and respects the Clements family's need for answers and asks for patience while the state police completes its investigation and the Cook County state's attorney conducts its review."