Newly released surveillance footage shows an off-duty Chicago police officer shooting and wounding an unarmed autistic black teenager in an incident the police department described as an armed confrontation.

The videos, released on Tuesday by the Civilian Office of Police Accountability, the city’s police oversight agency, shows officer Khalil Muhammad shooting 18-year-old Ricardo “Ricky” Hayes early in the morning on August 13, 2017. Hayes can be seen running along the pavement before stopping. Muhammad pulls up alongside, with parked cars between them. Hayes takes a few steps towards him and Muhammad shoots the teen in the arm and chest. Hayes turns and runs, despite his injuries.

A lawsuit filed earlier this year on behalf of Hayes said the teenager’s caretaker reported Hayes missing and described his “intellectual and developmental disabilities” to police. Local media reported Hayes has autism.

Shortly after the incident, the American Civil Liberties Union (ACLU) filed a lawsuit that cited the shooting and challenged “the city’s failure to train and monitor officers to ensure they safely interact with people with disabilities”.

Karen Sheley, the director of ACLU of Illinois, said in a statement on Tuesday that video “shows both that there was no justification for the officer to shoot him (Hayes) and that initial stories told by the CPD officials about the shooting – that the ‘encounter escalated’ – were false”.

She added: “As a black teenager with disabilities, Ricky was at a heightened risk for police violence. Thankfully, he survived – but he should never have been shot.”

The audio files included the sergeant’s call to 911 after he shot Hayes.

“The guy, like, he was about to pull a gun. Walked up to the car, and I had to shoot,” Muhammad told a Chicago Fire Department dispatcher.

Police Superintendent Eddie Johnson later said Hayes had no weapon.

In a statement, COPA said it delayed releasing the video and related material because of concerns about the legality of releasing information related to wards of the state.

Chicago police spokesman Anthony Guglielmi said on Tuesday that Muhammad is on administrative leave pending the outcome of the COPA investigation.

Pattern of excessive force

The release of the footage comes less than a month after Jason Van Dyke, a white Chicago police officer, was convicted of second-degree murder in the shooting of Laquan McDonald, a 17-year-old African American.

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Van Dyke shot McDonald 16 times in October 2014, as the teen, who was carrying a knife, appeared to be walking away from him.

The video from that shooting, which was released via a Freedom of Information Act request, prompted the Federal Department of Justice to investigate the Chicago Police Department. The probe’s report in 2017 found that the department shows a pattern of using excessive force and civil rights violations.

According to the Washington Post’s Fatal Force database, at least 750 people have been killed by the police in the US this year. The Post found that more than 980 people were killed by police in 2017.

The Guardian identified more than 1,090 police killings the previous year.

Nearly a quarter of those killed by police in 2016 were African Americans, although the group accounted for roughly 12 percent of the total US population.

According to watchdog group The Sentencing Project, African American men are six times more likely to be arrested than white men.

These disparities, particularly the killing of African Americans by police, has prompted the rise of the Black Lives Matter movement, a popular civil rights movement aimed at ending police violence and dismantling structural racism.