The highly unusual suit was filed on Friday in the middle of the city's effort to grapple with serious questions about the future of its police force.
The timing and unusual nature of the suit by officer Robert Rialmo, who is seeking $US 10 million ($A13.92 million) in damages, could complicate the department's efforts to demonstrate more sensitivity toward the community in how police shootings are handled.
His lawyer, Joel Brodsky, said it was important in the charged atmosphere to send a message that police are "not targets for assaults" and "suffer damage like anybody else".
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The teen's father, Antonio LeGrier, filed a wrongful death lawsuit days after the December 26 shooting, saying his son, Quintonio, was not armed with a weapon and was not a threat.
His lawyer, Basileios Foutris, was incredulous at what he called 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."
The lawsuit provides the officer's first public account of how he says the shooting happened, offering details that differ with the family's version.
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It says Rialmo, who was responding to a domestic disturbance call with another officer, opened fire after Quintonio LeGrier swung a bat at the officer's head at close range.
A downstairs neighbour, 55-year-old Bettie 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 filing says.
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