US policeman Jason Van Dyke charged with murder had 20 earlier complaints

It's for the first time a Chicago police officer has been charged with first-degree murder.

Chicago: A white Chicago policeman caught on tape shooting dead a black teenager had at least 20 complaints filed against him but was never disciplined, a database shows, in the latest such incident to inflame racial sentiment in the US.

The graphic video released shortly after officer Jason Van Dyke was charged with first-degree murder Tuesday has also reignited impassioned debate about the use of force by law enforcement in the United States, with Chicago left dangerously on edge.

Protesters there have likened the Laquan McDonald killing to that of Michael Brown, the black teenager shot dead by a white policeman in Ferguson, Missouri last year, triggering 15 months of demonstrations in major US cities over perceived police brutality against black men.

Chicago police initially said that McDonald was high on the hallucinogen PCP, acting erratically and lunged at officers with a knife when he was shot 16 times in October 2014.

But the dashcam video showed the 17-year-old walking away when Van Dyke opened fire and made no threatening gestures to justify the use of deadly force, prosecutors said in announcing the charges.

It was the first time a Chicago police officer has been charged with first-degree murder for an on-duty fatality in more than 30 years, the Chicago Tribune reported.