A Chicago policeman who shot dead a teenager and accidentally killed a neighbour is seeking $10m (£7m) damages from the boy's family.
Robert Rialmo claimed the shooting in Chicago on 26 December left him traumatised.
The officer has now filed a lawsuit against the relatives of 19-year-old black student Quintonio LeGrier.
In the days after the death, the victim's father Antonio LeGrier filed a wrongful death lawsuit, saying his son was not armed with a weapon and was not a threat.
His lawyer Basileios Foutris has criticised the officer's "temerity" in suing the grieving family.
He said: "That's a new low even for the Chicago Police Department. First you shoot them, then you sue them."
Rialmo has given his first public account of how he said the shooting happened, including details different to the family's version of events.
He and another officer were responding to a domestic disturbance call at a two-storey apartment building in the city.
Quintonio LeGrier ran downstairs and swung a baseball bat at Rialmo's head, missing it by inches, according to the lawsuit.
The officer told the teenager to drop it but the youth tried to hit him again at close range and when he raised his bat for a third time, the officer pulled out his 9mm handgun and opened fire, it added.
Neighbour Bettie Jones, 55, who was standing nearby, was shot and killed by accident and was not part of the dispute, it went on.
Lawyers for Antonio LeGrier and Jones say the evidence indicates Rialmo was 20 to 30ft away when he fired, calling into question the officer's claim he feared for his life.
The legal action comes at a time when the police force is trying to win back public trust after a number of deadly shootings, including several cases of alleged officer misconduct.
Rialmo's lawyer Joel Brodsky said it was important to send a message that police are "not targets for assaults" and "suffer damage like anybody else".
But the lawsuit could complicate the department's efforts to demonstrate more sensitivity towards the community in how police shootings are handled.