A grand jury on Monday declined to indict police officer Darren Wilson in the fatal shooting of an unarmed black teenager, resolving a secretive, months-long legal saga and reigniting powerful frustrations about America’s policing of African Americans.

The decision means that Wilson, 28, will face no state charges for the Aug. 9 shooting of 18-year-old Michael Brown. It also set off a show of fury on streets near where Brown was shot, a reflection of emotions that register in this riven city as either out of control or justifiable.

At least two police cars and a half-dozen buildings were set aflame. Not far from Christmas lights in downtown Ferguson that read “Seasons Greetings,” police fired tear-gas canisters to contain the crowds. People looted liquor and convenience stores, a response that ran counter to the peace that Missouri authorities, President Obama and Brown’s family had requested.

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As St. Louis County Prosecuting Attorney Robert P. McCulloch announced the decision, National Guard troops fanned out across the city. There was calm and silence in the streets of Ferguson for a half-beat after the announcement, but anger erupted shortly thereafter, and just after midnight county police reported hearing automatic-weapon fire. Protestors also blocked Interstate 44, causing a miles-long back-up of traffic.

In a sign of the way that the events from Ferguson have both compelled and startled a nation, protesters also gathered in front of the White House as well as in major cities from coast to coast, with sporadic reports of police cars being attacked.

Well after midnight, firefighters were tending to the embers of several buildings. “Citizens, go home,” police standing on West Florissant Ave. said over a loudspeaker, and by that time most had. At a 1:30 a.m. press conference, St. Louis County police chief Jon Belmar said he felt “very uplifted that we didn’t have any loss of life,” according to the local media on hand.

Though many in St. Louis expected that Wilson would not be indicted, officials here faced a challenge in trying to provide rationale for that decision. McCulloch, during a news conference, emphasized that testimony varied sharply among eyewitnesses and made it difficult to have a clear account of what unfolded during the 90-second confrontation between Wilson and Brown on Canfield Drive.

“Hands up, don’t shoot” has become a rallying cry in recent month for protesters, but McCulloch said that even the image of Brown’s surrender may have been a fiction.

“Some witnesses maintained their original statement that Mr. Brown had his hands in the air and was not moving toward the officer when he was shot,” McCulloch said. “Several witnesses said Mr. Brown did not raise his hands at all or that he raised them briefly and then dropped them and then turned toward Officer Wilson, who then fired several rounds.”

A statement from Wilson’s attorneys released shortly after the grand jury announcement said that officers must sometimes make “split-second and difficult decisions” and that Wilson “followed his training and followed the law.” The statement didn’t mention Brown.

President Obama, speaking after the grand jury announcement, urged peace in St. Louis, as did many authorities in the region. The president also asked officers in Ferguson to show restraint. But Missouri Gov. Jay Nixon (D) warned that “if people are violent or threatening property, then resources will be used.”

A grand jury has declined to indict Ferguson, Mo., police officer Darren Wilson in the shooting death of 18-year-old Michael Brown. Here is a look back at the events following the August shooting. (Gillian Brockell and Sarah Parnass/The Washington Post)

For more than three months, the grand jury — made up of seven men and five women, nine white and three black — heard evidence into the shooting. They met 25 times and heard from 60 witnesses, McCulloch said. They considered charges ranging from first-degree murder to involuntary manslaughter. In a criminal trial, jurors must decide a crime has been committed beyond a reasonable doubt. But here, those jurors needed only to feel there was probable cause that Wilson had committed a crime.

“We are profoundly disappointed that the killer of our child will not face the consequence of his actions,” the Brown family said in a statement released after the announcement.

A trove of evidence from the proceedings was released late Monday night, but beforehand McCulloch tried to describe the encounter between Wilson and Brown. He said that during the incident, Wilson angled his vehicle to block the path of Brown and friend Dorian Johnson. Two shots were fired while Wilson still sat in the car, and Brown’s blood was found inside the vehicle. McCulloch said, referencing witnesses, that some kind of “tussling” or “tug of war” took place.

Brown then ran east on Canfield, and Wilson gave chase. “Less than 90 seconds passed” during the entire encounter, McCulloch said. Ten shots were fired after Brown fled, and Brown was hit seven or eight times.

In an interview with the St. Louis County Police Department one day after the shooting, Wilson said that Brown had begun the encounter by leaning into the squad car’s driver’s-side door while Wilson was still inside — a way to prevent the officer from getting out. The dispute turned physical, and Wilson, who couldn’t reach his mace, drew his firearm. Brown managed to grab it, Wilson said.

“I was guaranteed he was going to shoot me,” the officer said, in an interview that was released along with other grand jury evidence. “He had completely overpowered me while I was sitting in the car.”

Among the documents released Monday, one showed Wilson in the hospital — presumably right after the shooting — standing and looking head-on at the camera. One of his cheeks was red, but not heavily bruised, in contrast with rumors after the shooting that suggested he had a broken or cracked orbital socket.

Officials had discussed emergency plans in the event of a violent reaction, while protest organizers and community leaders mapped out their response in the hopes of avoiding the unrest that exploded after Brown was killed. Brown’s family had asked for 4.5 minutes of silence after a grand jury decision was announced — symbolic of the 4.5 hours Brown’s body remained on the street after the shooting.

Hundreds had gathered on South Florissant Road, a main area of commerce in Ferguson. The windows of a law firm and a video store were smashed. Fuel fed fire in a garbage can, and protesters were wiping their faces of what they said was tear gas. The Ferguson police department, where Wilson worked, is also on South Florissant.

“I know how outraged and upset people are, but where’s the justice in this?” said Rosalind Hagedorn, a homemaker who came out to join the demonstration in front of police headquarters, pointing at a Beauty World shop with smashed windows. She said she has lived here for more than 30 years and shopped at that store. “I understand the emotion, but these people did nothing,” she said.

U.S. Attorney General Eric H. Holder Jr. on Monday night called Brown’s death a “tragedy” that has “sparked a national conversation about the need to ensure confidence between law enforcement and the communities they protect and serve.”

The grand jurors convened in mid-August, days after the shooting, and spent weeks considering the case. Discussions could have stretched on even longer; the panel had been granted an extension through early January.

Impatience and pressure for a decision have been building among residents and business owners, as well as police officers, who have been working 12-hour shifts with all leave time canceled since Saturday, said Jeff Roorda, business manager for the St. Louis Police Officers Association. That schedule will continue through the aftermath of the grand jury’s decision.

The closed-door grand jury process, much like the initial investigation, has been controversial. Opponents had asked McCulloch to recuse himself from the case over perceived biases; McCulloch’s father, a police officer, was killed on the job by an African-American.

Sarah Larimer and Jerry Markon in Washington contributed to this report.