What has happened?
The grand jury investigating the August shooting of unarmed black teenager Michael Brown in the St Louis suburb of Ferguson decided not to indict white police officer Darren Wilson.
At around 8pm local time, St Louis County prosecutor Bob McCulloch announced the news outside the Buzz Westfall Justice Centre in nearby Clayton.
The grand jury of 12 people had been asked to decide whether there was “probable cause” to indict Officer Wilson on a number of charges, ranging from involuntary manslaughter to murder.
They found that “no probable cause" existed to file any charge against Officer Wilson.
Mr McCulloch said witness statements in the aftermath of the shooting varied considerably from the physical evidence of the scene and he praised the jury for their diligence.
What has been the response?
Protests broke out again in Ferguson with shots being fired and buildings set alight with police using tear gas to break up crowds.
Groups of protesters were seen chanting "hands up, don't shoot" - in reference to statements by witnesses who said those were the words of Brown before he was shot.
Thousands of people also marched in various cities across the country - in Boston, Chicago, Los Angeles, New York, Oakland, Philadelphia, Seattle and Washington DC.
A state of emergency had already been announced by governor Jay Nixon in anticipation of the decision and national guard troops have been drawn in to protect fire stations, police stations and utility substations.
It is hoped the protests will be more peaceful than those seen in Ferguson in the immediate aftermath of Brown's death with activist groups urging people to engage in "non-violent civil disobedience".
What has been said?
Barack Obama made a televised address to the nation last night urging for calm and called on his compatriots to accept the decision the grand jury has made.
He said he had asked the outgoing US Attorney General, Eric Holder, “to engage nationally in a conversation between law enforcement and communities of colour... Lack of trust between communities and law enforcement crops up not just in Ferguson, but in places all across the country.”
The family of Michael Brown said they are "profoundly disappointed that the killer of our child" was not indicted.
In an earlier statement they said:
We are not here to be violent. We are here in memory of our son. We are here for protection of all children. We are here to support justice and equality for all people. We lift our voices to ensure black and brown men, women and children can live in this country without being devalued because of the colour of our skin.