Missouri grand jury decided not to indict Darren Wilson, a white police officer who shot and killed Michael Brown, an unarmed black 18-year-old, touching off violent protests in Ferguson.

The decision in the closely watched case was announced Monday night. Hundreds of demonstrators erupted into the streets around the Ferguson police station minutes after the announcement, smashing windows and torching cars. As the hours passed, at least three buildings were ablaze and several businesses were looted. Shots were also fired.

Police responded with what appeared to be tear gas.

Prosecuting Attorney Robert P. McCulloch was emphatic in his announcement. “Our investigation has been completed,” he told reporters. After detailing the grand jury's work, he said that “no probable cause exists” to charge Wilson on any of the five charges he could have faced.

The Brown family said in a statement that “we are profoundly disappointed that the killer of our child will not face the consequence of his actions.”

Brown’s parents, Lesley McSpadden and Michael Brown, urged peaceful demonstrations.

“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,” said Brown’s parents, who will hold a news conference Tuesday.

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

President Obama joined with Brown’s family in urging peaceful protests, and he also cautioned police to show restraint.

Obama said he understood the frustration in minority communities surrounding the case of a black man fatally shot by a white police officer.

“This is not just an issue for Ferguson. This is an issue for America,” Obama said at the White House. “We do have work to do here, and we shouldn’t try to paper over it.”

The scene outside the Ferguson Police Department turned violent after several hundred demonstrators began to jostle one another after the decision was announced. Clouds of what appeared to be tear gas filled billowed through the air.

“Our lives don’t matter! Our lives don’t matter! Our lives don’t matter,” protesters shouted.

Dozens of police officers stood behind metal barricades outside the building. Scores of people ran up to the barricades and shouted insults at them and at riot police filing out of the station.

Several riot police hurried to take up a position farther from the crowd.

“I will do everything in my power to keep you safe and protect your right to speak,” Missouri Gov. Jay Nixon said in a statement directed at residents. “We must also make a commitment to one another: to trust more and fear less, to hold ourselves to a higher standard of personal responsibility and mutual respect, and to keep working to extend the promise of America to all our citizens.

“It is my continued hope and expectation that peace will prevail. The world is watching,” he said.

Wilson’s fatal shooting of Brown on Aug. 9, after a brief struggle at Wilson’s police car, prompted months of protests in Ferguson, a predominantly black city of 21,000 with a predominantly white government and police force.

Tension, which had been growing in recent days as the grand jury moved to complete its work, became even more intense Monday. New barricades were erected around the Justice Center in Clayton, the county seat of St. Louis County, where Ferguson is located.

The Federal Aviation Administration placed temporary flight restrictions over Ferguson after deeming it a hazardous area. No media helicopters or commercial flights were allowed in a three-mile radius up to an altitude of 3,000 feet.

In New York, about 2,000 people covering four blocks marched through the streets of midtown Manhattan calling for justice. They were of all ages and races, but mainly young adults. “Justice for Mike Brown. Justice for Mike Brown,” they chanted to the sound of a few drums.

There was a constant police presence, but it was low key.

*Text excerpted from a Los Angeles Times report.