NEW YORK

 Grieving relatives and friends of two people fatally shot by Chicago police are demanding changes to the city's policing strategies, saying its law-enforcement officers have failed the public.

Police have said 55-year-old Bettie Jones, a mother of five, was "accidentally" killed by an officer responding to a report of a domestic dispute early Saturday morning.

Engineering student Quintonio LeGrier, 19, was also killed in the incident.

"Upon arrival, officers were confronted by a combative subject resulting in the discharging of the officer's weapon which fatally wounded two individuals," Chicago police said in a statement e-mailed to U.S. media.

"The 55-year-old female victim was accidentally struck and tragically killed. The department extends it's [sic] deepest condolences to the victim's family and friends," it added.

In a press conference on Sunday, the victims' families and friends blamed a police approach of "shoot first and ask questions later" for the deaths of Jones and LeGrier.

"This needs to stop," LeGrier's mother, Janet Cooksey, told reporters. 

"No mother should have to bury her child, especially under these circumstances. The police are supposed to serve and protect us," she said, as quoted by CNN. She added that the Chicago police had failed her and many others. 

Saturday's double shooting occurred after LeGrier threatened his father with a baseball bat, which led the man to call 911, according to the teen's family.

Antonio LeGrier then called his downstairs neighbor, Jones, to open the door when officers arrived. He told the Chicago Sun-Times newspaper that he heard gunshots and found the victims lying in the foyer when the police arrived.

Both Jones and Quintonio LeGrier were black.

Chicago Mayor Rahm Emanuel said an investigation had been launched.

The city is already under a Justice Department investigation into its policing tactics, including what it calls a use of deadly force, “racial and ethnic disparities in officers' activities, and accountability mechanisms”.

Saturday's double shooting came on the heels of angry protests following the release of a police dashcam video showing a white officer fatally shooting a 17-year-old black teenager, Laquan McDonald, 16 times.

Protests led to the firing of police chief Garry McCarthy on Dec. 1.

The cases in Chicago are among a string of high-profile, police-linked killings of black suspects that have stirred racial tensions and set off nationwide protests over perceived prejudices within the U.S. justice system.