(CHICAGO) A woman filed a lawsuit against the City of Chicago and several Chicago Police officers Thursday, alleging the officers who killed her son on Christmas 2014 used excessive force and conspired to cover up their misconduct.

Sharon Woodall filed the lawsuit against the city and unknown officers in U.S. District Court.

Her son, Terrance Gilbert, 25, was on the front porch of his aunt’s home in the 400 block of East Marquette Road around 6:40 p.m. on Dec. 25, 2014 when officers fatally shot him, according to the lawsuit.

Gilbert — who police said was suicidal — lunged at the officers with a knife and struck the protective vest of one of the officers twice, police said at the time. After officers asked him to drop the knife, he again lunged at the officers with the knife as he was walking away eastbound.

He was shot twice in the torso and was pronounced dead at 9:02 p.m. at Stroger Hospital, authorities said. An injured officer was also taken to an area hospital and treated for minor injuries.

The six count lawsuit seeks “an amount reasonable to compensate [Gilbert’s] estate, plus punitive damages against [the officers], in addition to costs, attorney’s fees, and such other relief as is just and equitable.”

In addition to the counts of excessive force and conspiracy, the suit alleges that the city encourages this kind of misconduct because it does not adequately discipline officers. The last three counts in the suit invoke the Illinois Wrongful Death Claim and the Illinois Survival Act Claim.

Bill McCaffrey, a spokesman for the city’s Law Department, said the city had not yet reviewed the lawsuit and declined to comment.