CHICAGO (CBS) — The family of 17-year-old Michael Elam Jr., who was shot and killed by a Chicago police officer in February, has filed a lawsuit against the city, accusing the officer of “unreasonable and unjustifiable excessive force.”

Elam was supposed to graduate from West Town Academy High School on Friday, but instead his family has filed a federal lawsuit against the city and the officer who shot and killed him.

The lawsuit identifies the officer who shot Elam as Adolf Bolanos, and accuses the officer and the city of excessive force and wrongful death. Attorney Jeffrey Neslund said Elam was unarmed and running away from police when Bolanos shot him once in the back of the head and twice in the lower back.

That contradicts the Chicago Police Department’s initial account of the shooting.

Police have said, around 8:30 p.m. that day, officers were trying to make a traffic stop near 21st and Keeler, when the car crashed into a parked vehicle. Police Department spokesman Anthony Guglielmi stated on Twitter that “armed individuals exited the car and got into a confrontation with officers,” when police shot Elam.

Guglielmi said a weapon was recovered at the scene, and tweeted a photo of a gun next to an evidence marker.

The Elam family’s lawsuit acknowledges the teenager began to flee police after the crash, but states he was “unarmed and not a threat to anyone” when Bolanos shot him.

“The acts of Defendant Bolanos were a deliberate and malicious deprivation of the Plaintiff’s Constitutional rights against excessive force,” the lawsuit alleges. “As a result of the unreasonable and unjustifiable excessive force used by the Defendant Bolanos, Michael Elam suffered fatal injuries.”

The lawsuit also claims Bolanos failed to activate his body camera as required by Chicago Police Department policy. Neslund said there is body camera footage from Bolanos’ partner and other officers who responded to the scene, but the videos do not show the actual shooting.

Neslund said the video shows officers waited five to six minutes before informing police dispatch there had been a shooting, and requesting an ambulance. He said the video footage shows police searching Elam after he was shot, and finding only a cell phone and ear buds.

The Civilian Office of Police Accountability is investigating the shooting.

Neslund called on the FBI and U.S. Attorney’s office to investigate the shooting, saying COPA and the Cook County State’s Attorney’s office have a poor track record of investigating Chicago police shootings.

Neslund also represented the family of 17-year-old Laquan McDonald, who was shot and killed by Officer Jason Van Dyke, and negotiated a $5 million settlement with the city without even filing a lawsuit, Van Dyke is serving a 6-year, 9-month prison sentence for second-degree murder in McDonald’s death.