A WHITE Chicago police officer who fatally shot a black teenager and accidentally killed a neighbour is now suing the teen’s estate, saying the shooting has left him traumatised.

Engineering student Quintonio LeGrier, 19, was shot and killed on December 26 near his home in the Chicago neighbourhood of West Garfield Park as police responded to a disturbance involving LeGrier and his father.

Bettie Jones, a 55-year-old mother of five who lived in the same building as LeGrier, was “accidentally struck and tragically killed” by a police bullet during the incident, according to a statement from the Chicago Police Department.

LeGrier’s father Antonio LeGrier filed a wrongful-death suit after his son’s death, saying Quintonio was not armed with a weapon and was not a threat.

But in a bizarre twist, officer Robert Rialmo, who fatally shot LeGrier, filed a counterclaim on Friday and is seeking $US50,000 ($A70,800) for physical and emotional trauma and $US10 million ($AU14 million) in punitive damages.

The lawsuit comes as Chicago police are called into question over its system for investigating police shootings following several cases of alleged misconduct.

Chicago’s mayor has promised a major overhaul of the police department to heal its fraught relationship with black residents.

The lawsuit also provides Rialmo’s first public account of how he says the shooting happened, which contradicts the LeGrier family’s version of events.

Rialmo said he was responding to a domestic disturbance call with another officer and opened fire after LeGrier swung a bat at the officer’s head at close range.

Jones was standing nearby and was shot and killed by accident. She was not part of the domestic dispute.

“The fact that LeGrier’s actions had forced Officer Rialmo to end LeGrier’s life and to accidentally take the innocent life of Bettie Jones has caused, and will continue to cause, Officer Rialmo to suffer extreme emotional trauma,” the document says.

But Antonio LeGrier’s lawyer Basileios Foutris said he was incredulous at the officer’s “temerity” in suing the grieving family of the person he shot.

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

Rialmo’s lawyer Joel Brodsky said it was important to send a message that police were “not targets for assaults” and “suffer damage like anybody else.”

According to Rialmo’s suit document, the officer arrived at the scene about 4.30am and was let into the building by Jones. He then he saw LeGrier charging down the stairs with a baseball bat and “took a full swing at Officer Rialmo’s head, missing it by inches” when the two were around 1.2 metres apart.

The officer then backed away with his weapon still holstered, according to the suit, while repeatedly shouting at LeGrier to drop the bat.

But the suit says LeGrier kept advancing and swung the bat again. Only when LeGrier cocked the bat again from three or four feet away, did the officer pull out his 9mm handgun and open fire, the filing says.

As he began firing, Rialmo did not see or hear Jones behind LeGrier, the suit says. It says one of the bullets went through LeGrier’s body and struck Jones, killing her.

An autopsy determined that LeGrier suffered six bullet wounds.

Lawyers for Antonio LeGrier and Jones have provided accounts that differ from Rialmo’s. They say the evidence indicates the officer was six to nine metres away when he fired, calling into question Rialmo’s contention that he feared for his life.

Foutris also questions why the teen would attack the officer since he was the one who called police.

County prosecutors have asked the FBI to investigate the shooting.

while the US Justice Department is conducting a wideranging civil rights investigation.