Thousands of people rallied in US cities including Los Angeles and New York to protest a grand jury’s decision not to indict a white police officer who killed an unarmed black 18-year-old in Ferguson, Missouri.

Gunshots rang out and police lobbed tear gas at an angry crowd in suburban St. Louis after the grand jury decision was announced late on Monday.

Angry protesters overran barricades and taunted police in Ferguson, with some chanting “murderer” and others throwing rocks and bottles, as police car windows were smashed and protesters tried to set vehicles ablaze.

Officers responded by firing what authorities said was smoke and pepper spray into the crowd, as some in the crowd tried to stop others from taking part in the violence.

Activists had been planning to protest even before the nighttime announcement that officer Darren Wilson would not be charged in the shooting death of Michael Brown on August 9.

Wilson shot Brown at least 12 times according to evidence presented to the grand jury, with witness reports differing as to whether and when Brown had his hands raised.

‘Black lives matter’

In New York City marchers chanting “Black lives matter” snarled traffic on Broadway through Times Square.

In Chicago, demonstrators walked up Lake Shore Drive carrying banners that read “Justice for Mike Brown”.

Police in Ferguson used smoke canisters and trucks to force waves of violent protesters down the street away from the police building soon after sporadic gunshots were heard. Flames from a burning car rose into the night sky.

Whistles pierced the air as some of the hundreds of protesters tried to keep the peace, shouting, “Don’t run, don’t run.”

Police who formed a wall of clear riot shields outside the precinct were pelted with bottles and cans as the crowd surged up and down the street immediately after authorities said the grand jury had voted not to indict Wilson.

“Murderers, you’re nothing but murderers,” protesters in the crowd shouted. One woman, speaking through a megaphone said, “Stinking murderers.”

Dozens of police and military vehicles were poised for possible mass arrests not far from the stretch of Ferguson streets that saw the worst of the rioting after Wilson shot Brown in August.

“They need to feel the pain these mothers feel at the (expletive) cemetery,” shouted Paulette Wilkes, 40, a teacher’s assistant who was in the crowd at the police department.

A smaller, calmer crowd of about three dozen protesters gathered outside the courthouse where the grand jury had met. In that crowd, a white woman held a sign that read: “Black Lives Matter.” Many of the protesters looked stunned.

“That’s just how the justice system works – the rich are up there and the poor are down here,” said Antonio Burns, 25, who is black and lives in the Ferguson area. The police “think they can get away with it,” Burns said.

A handful of Amnesty International volunteers in bright vests tried to maintain the peace.

‘Rightfuly angry’

Speaking to Al Jazeera, Dante Barry, executive director of Million Hoodies for Justice, said the protesters were “rightfully angry”.

“There is this misconception that we are living in a post-racial society. Even with a black president, it [police killings of African Americans] is still happening under his watch.

“What you’re seeing tonight is folks expressing frustration and it’s rightfully so.”

Al Jazeera’s Tom Ackerman, reporting from Washington D.C., said the evidence used by the grand jury for their decision will be published.

“Now that the case is closed, the evidence will be made public, including audio recordings and transcripts of the testimonies, which is not usual.”

Brown’s family quickly urged a non-violent response to the grand jury’s decision. In a statement released shortly after the decision the family said: “We are profoundly disappointed that the killer of our child will not face the consequence of his actions.”

“While we understand that many others share our pain, we ask that you channel your frustration in ways that will make a positive change. We need to work together to fix the system that allowed this to happen,” the statement added.

“We respectfully ask that you please keep your protests peaceful. Answering violence with violence is not the appropriate reaction. Let’s not just make noise, let’s make a difference,” it said.

Officials urged tolerance and assured residents that the National Guard would provide security at critical facilities like fire houses, police stations and utility substations.

“I do not want people in this community to think they have to barricade their doors and take up arms,” St. Louis County Executive Director Charlie Dooley said before the grand jury’s decision was announced. Al Jazeera