A white police officer from Chicago, who fatally shot a black 19-year-old college student, has filed a lawsuit against the teenager's family because he says he is "traumatised" by the shooting.

Officer Robert Rialmo, 27, filed the suit on Friday and is seeking $10 million in damages. His attorney said it was important to send a message that police are "not targets for assaults" and "suffer damage like anybody else."

Mr Rialmo claims he opened fire after Quintonio LeGrier swung a bat at the officer's head from close range. A neighbour, Bettie Jones, a 55-year-old mother of five, was standing nearby and was shot and killed by accident.

Lawyers for Mr LeGrier and for Mrs Jones have provided accounts that differ from Mr Rialmo's.

The teen's father, Antonio LeGrier, filed a wrongful death lawsuit days after the shooting, saying his son, was not armed with a weapon and was not a threat.

His attorney, Basileios Foutris described the suit a new low for the Police Department.

"That's a new low even for the Chicago Police Department," he said. "First you shoot them, then you sue them."

Mr Foutris also questions why the teen would attack the officer since he was the one who called police. The father of the Northern Illinois University student also made an emergency call to police.

"If you're calling multiple times for help are you going to charge a police officer and try to hit him with a bat? That's ridiculous."

The suit comes as the Mayor Rahm Emanuel has promised a major overhaul of the Police Department and steps to heal its fraught relationship with black residents.

Additional reporting by Associated Press.