(CBS) – The family of an 18-year-old Chicago man killed in a police-involved shooting – an incident that has resulted in three officers being stripped of their police powers – has filed a federal civil-rights lawsuit.

The wrongful-death lawsuit, filed Monday, alleges that police officers effectively “executed” Paul O’Neal when they curbed an allegedly stolen vehicle near 73rd and Merrill last Thursday, attorney Michael Oppenheimer said at a news conference at the shooting site.

O’Neal ran from the vehicle after officers fired into it, Oppenheimer said. The 18-year-old was struck in the back of the head by gunfire, he said; the Cook County Medical Examiner’s Office said he was shot in the back and have classified the death as a homicide.

“These police officers decided, for whatever reason, they were going to play judge jury and executioner,” Oppenheimer said.

He said it’s not clear if there is body-cam video of the fatal shooting, even though the police department equipped the officers with new equipment. He said the apparent failure smacks of a cover-up.

A police spokesperson said the body cameras of two officers who fired into the vehicle were working, but the body camera of the officer who fired the fatal shot was not working.

O’Neal was a recent high school graduate and was a good kid but lacked a father figure in his life, family spokesperson Ja’Mal Green said. He said if O’Neal had broken the law, the court system should have meted out justice, not the officers who fired their weapons. O’Neal was unarmed, Oppenheimer says.

The suit is against the unnamed officers who were involved in the fatal shooting.

Chicago Police Supt. Eddie Johnson has stripped three officers of their police powers, pending investigations. He said department policy was not followed but has not elaborated.