A Chicago police sergeant filed a whistleblower lawsuit against the department on Monday, claiming that superiors ordered him to falsify a report about an officer’s shooting of an autistic teenager.

Sgt. Isaac Lambert was assigned to investigate the shooting of unarmed 18-year-old Ricardo Hayes, who was wounded in August 2017 when he was shot twice at a distance by off-duty police Sgt. Khalil Muhammad. Lambert claims he was asked to mischaracterize the shooting as “an aggravated assault” against Muhammad by Hayes.

Hayes, who is autistic, was reported missing earlier that day by his “caretaker,” and was “skipping and running in the area, near where he lived” about 5 a.m. when he was spotted by Muhammad, who began to follow the teen in his vehicle, according to the lawsuit, filed in Cook County Circuit Court in Chicago .

Muhammad reportedly called Hayes over to the vehicle, but the teen allegedly moved only about four steps. In an incident report filed by Muhammad, he describes the teen as handling a “dark object perceived to be a gun.”

While he was still sitting in his vehicle, Muhammad began shooting at Hayes, who was hit twice in his left shoulder and side, the lawsuit alleges. The officer chased the teen until he apprehended him, then called 911 and “falsely reported that he was forced to shoot Ricardo because the young man walked up to his car and tried to pull a gun on him,” according to the complaint.

The shooting was captured on video by a home security camera, which allegedly shows that the shooting was “not justified and that Ricardo never did anything to threaten Muhammad.”

A lawsuit was filed in 2018 on behalf of Hayes’ estate, which claimed that he “functions at the cognitive level of a child, and he has difficulty communicating. Ricky looks much younger than his age and his disabilities are immediately recognizable.” That lawsuit is still pending, according to federal court records.

“They were going to try to pin this on this poor kid. It's shocking,” Gabriel Hardy, who represents Hayes, told The Daily Beast.

Lambert, a 25-year veteran of the department, claims that he was asked by superiors to incorrectly classify Muhammad as a “victim” in the case, even though he “was not able to provide a coherent or believable explanation for why he shot Ricardo” when police interviewed him on the night of the encounter, according to Monday’s lawsuit.

“ The Chicago Police Department has learned nothing from the fiasco surrounding its handling of the murder of Laquan McDonald. ” — Lambert’s attorney

“The police hierarchy wants the public to believe that this was a justified shooting by an officer who was being assaulted, when in fact it resembled a drive-by shooting of an innocent, disabled and unarmed young man,” said Torreya Hamilton, Lambert's attorney.

Five days after Lambert approved the report without the recommended changes from his superiors, he was removed from the detective division and back to a shift in the patrol division.

The department did not immediately respond to a request for comment.

The lawsuit, which was first reported by WBEZ radio, claims that “efforts were made by high-ranking officials in the Chicago Police Department to mischaracterize the findings of the investigation and change some of the conclusions.”

“Lambert’s removal from the detective division was because he refused to participate in an effort to cover up the illegal conduct of Muhammad towards Hayes and because he refused falsify police reports in order to mischaracterize a police shooting,” the lawsuit claims.

Hayes continues to struggle with his injuries, almost two years on, according to his attorney.

“Since then, he's had significant mental health issues,” Hayes said. “It's a piece of trauma that he's just not equipped to handle. The results have been devastating for him. He's been hospitalized several times.”

The lawsuit comes three days after federal oversight began for the city’s police department. An independent monitor and a federal judge were both named on March 1, and they will enforce the department’s implementation of a “consent decree” with the Justice Department to curb department's use of force, ban officers from using Tasers on people who are running away, and more.

Superintendent Eddie Johnson told reporters on Friday that he welcomes the overhaul.

"We've known about this consent decree for the last two years, so we're prepared mentally to have to deal with it," Johnson told NPR. "Matter of fact, the consent decree will make us better. We say bring it on and let's get down to business."

The decree came after Chicago has been in the spotlight for nearly five years over the fatal shooting of black 17-year-old Laquan McDonald, who was killed by a white officer. Video of the encounter shows McDonald appearing to walk away from police with a knife in his hand.

Officer Jason Van Dyke, who shot McDonald, was sentenced to six years and nine months in prison over the shooting and its handling.

“The Chicago Police Department has learned nothing from the fiasco surrounding its handling of the murder of Laquan McDonald,” Lambert’s attorney Hamilton said in a statement on Monday.

“Sgt. Lambert had the guts and the integrity to refuse to participate in an effort to cover up a fellow officer's criminal behavior. He should be protected by the Department's brass, not punished."