Officer charged with 1st-degree murder 'abused his authority' in firing 16 shots at a teenager

Officials in Chicago have released video that they say shows the shooting death of a teenager by a Chicago police officer last year. The officer is charged with first-degree murder and accused by prosecutors of firing 16 shots as the teen was walking away from the officer.

Laquan McDonald, 17, was killed in the October 20, 2014, shooting.

The video shows an encounter between several police officers - including Jason Van Dyke - who were responding to a call of a man with a knife.

In the footage, which does not include audio, McDonald is first seen jogging toward arriving police officers, then begins to walk away from them.

Moments later, McDonald is shot and collapses. At least one shot appears to hit him as he lies motionless on the ground.

The Chicago police union has said McDonald was "behaving erratically and refusing officers' commands" to drop a knife he was holding. The police union's statement maintains that Van Dyke "fired in fear for his life" and that McDonald "lunged" at Van Dyke with the knife.

The Chicago Tribune reports that Van Dyke, 37, fired 16 bullets at McDonald within six seconds of leaving his squad car and was reloading his weapon before another officer told him to hold his fire.

The police released the video in response to a court order that the footage be made public by Wednesday.

You can see the graphic video below. The final encounter begins around the 5:22 mark:

Cook County prosecutor Anita Alvarez said on Tuesday, "Clearly this officer went overboard and he abused his authority." She added, "I don't think use of force was necessary."

City officials in Chicago appear to have distanced themselves from Van Dyke and the police union.

During a news conference on Tuesday, Chicago Mayor Rahm Emanuel said, "Jason Van Dyke does not represent the police department."

Van Dyke is no longer on the police department's payroll, according to department officials.

Additional surveillance video allegedly deleted

People have expressed concern about additional security footage from a nearby Burger King restaurant that may have captured the shooting.

NBC News Chicago cited lawyers for the McDonald family who said 86 minutes of video was missing from the recording after the police handled the footage.

The missing footage spans 9:13 p.m. to 10:39 p.m. on the night of the shooting, according to the lawyers cited by NBC News Chicago. McDonald was shot at 9:50 p.m.

Alvarez said forensic testing was done to determine whether the Burger King surveillance system had been tampered with and "did not reveal any such evidence."

Demonstrations continue in Chicago

Protesters have slammed the police union's claim that the shooting was justified. They are calling it an "execution."

Police shootings in the national spotlight

The fatal shootings of black men, women, and children by the police have caught national attention since the death of Michael Brown, an unarmed teen who was killed in Ferguson, Missouri, in August 2014.

Darren Wilson, the now former Ferguson police officer who shot Brown six times, including twice in the head, was not charged in the killing.

Demonstrations have spread across the country since Brown's killing as more black citizens, some of whom were unarmed, have been killed by the police, increasingly in encounters caught on video. In some cases, they died while in police custody.

Several cases remain pending, including that of Tamir Rice, a 12-year-old boy who was shot by a Cleveland police officer within seconds of that officer approaching him in November 2014.

Investigators are also looking into the death of Jamar Clark, who was shot by the police in Minneapolis on November 15. Witnesses say Clark was in handcuffs when he was shot. The police have disputed those claims. The FBI has begun a civil-rights investigation.