Even as the president, live from the White House, said “there is inevitably going to be some negative reaction, and it will make for good TV,” the news channels split their screens to show police shooting tear-gas canisters at protesters in Ferguson, Mo. — a presidential appeal for calm competing against frightening scenes of angry confrontation.

Monday night’s reaction to a grand jury’s decision not to indict the Ferguson police officer who killed an unarmed young black man in August consisted of peaceful protest in some places and vandalism and looting in others — a burst of violence so widely and persistently predicted that it seemed as much self-fulfilling prophecy as organic expression of rage.

Spontaneous or organized, riots have sporadically pierced the social compact through two and a half centuries of this country’s struggles over equality and opportunity. But August’s violence in Ferguson broke the mold in three important ways — one of which is just unfolding now. These were rare suburban riots, racial violence coming to the very place where many Americans — both white and black — had fled after the urban unrest of the 1960s. These were the most significant explosions of racial frustration since the election of the nation’s first black president, and so Ferguson forced the country out of the fantasy that America had entered a “post-racial” era.

Finally, what distinguishes Ferguson from the crowded historical catalogue of racially-motivated street violence is what has happened in recent weeks: The unseemly buildup to the announcement of the grand jury’s conclusion that no crime was committed in the shooting death of 18-year-old Michael Brown has produced an expectation of ugliness. What occurred Monday night — and may continue in the days ahead — is rioting as planned event, so pervasively predicted, so extensively prepared for as to obscure the power and meaning of the protests.

A news media obsessed with predicting the next step, a security apparatus equipped to put down almost any uprising, and a political power structure apparently seeking to head off violence by predicting it have combined to produce an unprecedented sense of inevitability, reducing what has historically been an explosion of frustration to a kind of staged performance.

From Missouri Gov. Jay Nixon’s declaration of a state of emergency to reports of soaring gun sales in the St. Louis area, from nonstop coverage on the cable news channels to new expenditures by St. Louis County police on riot gear, the assumption (fed by copious news leaks) that Darren Wilson, the white officer, would not be prosecuted led to an hourly drumbeat of preparations for mayhem.

Police officers’ vacations were canceled and schoolchildren were sent home with packets of homework designed to last them through several days of civil unrest.

The result was a pivot from the questions of justice and race relations that drove August’s protests to a more tactical debate over how to contain popular rage.

Thanks to a relentlessly forward-skewed news media — “What will happen next?” was the topic of nearly every cable news discussion — Monday night’s violence became on-demand programming for a nation that flits from one blockbuster event to the next.

The days of anticipation diminished the debate over solutions that the Brown shooting had initially revived. The Justice Department is still investigating police practices in Ferguson, the ACLU is still probing the Ferguson police department’s treatment of journalists who covered the August protests, and state officials are still looking at ways to reform law enforcement in the area.

But the complaints among black residents in Ferguson and beyond about police misconduct and courts that don’t seem to administer justice equally have not abated.

Communities around the nation regularly take to the streets to protest police shootings of unarmed black men; in Ferguson’s case, the anger and frustration that turned protests violent was born of a larger sense of disenfranchisement, a pervasive belief that some people — blacks, low-end workers, the unemployed — can’t get a break, can’t wedge a foot in the door.

The confrontation in Ferguson: Different stories

“We are a nation of two societies, one black, one white — separate and unequal,” the Kerner Commission famously concluded after the urban riots of the late 1960s. Since then, a large and successful black middle class has emerged, and many legal and cultural barriers to inclusion in the nation’s business and social endeavors have fallen away.

But the races remain sharply divided in important ways in both perception and reality. In a survey of St. Louis County residents a month after the initial violence, blacks and whites split over whether the shooting was justified (62 percent of whites said it was; 65 percent of black said it was not) and over whether Brown was targeted because of his race (77 percent of whites said no, 64 percent of blacks said yes.) The only thing a majority of both races agreed on was that the news media has made the situation in Ferguson worse, not better.

The violence in Ferguson has not so far, however, prompted the national debate that President Obama called for Monday night when he said, “We still have work to do here. . . . There are still problems, and communities of color aren’t just making those problems up.”

For protesters and those who agree with them, the death of Michael Brown has joined those of Eric Garner in New York, Trayvon Martin in Sanford, Fla., and Oscar Grant in a transit station in Oakland, Calif., in a roll call of young black men whose violent end is a reminder of the reservoir of mistrust and misapprehension that divides African Americans from those in charge of the state’s use of force. But for many other Americans, the most concerning aspect of the events in Ferguson has been the disorder in the streets.

Blacks are more than six times as likely as whites to say that police have discriminated against them because of their race, according to a CBS/New York Times poll taken after the Ferguson shooting. Combine that with the paucity of black officers in Ferguson, where about two-thirds of residents are African American, and a familiar plaint of powerlessness and frustration leads to the same kind of reaction that has followed other such police shootings of unarmed black men over the past half-century: study commissions, investigations, policy revisions, training programs.

In Ferguson, signs of change quickly followed the riots. The city decided in September to set up a citizen review board to monitor its police department, and the City Council moved to scrap a system in which court fines were used to fund a significant chunk of Ferguson’s budget. And St. Louis officials are considering a massive overhaul of the county’s system of dispersing political power to small municipal governments, which some say has contributed to inequalities of resources, power and administration of justice in the region.

The Brown family came to Washington in the fall to press for an anti-racial-profiling bill similar to one that followed the Rodney King episode in Los Angeles (that law required the FBI to track police brutality statistics but did not require local police forces to report them).

Efforts at the start of the 2000s to ban racial profiling in local policing — President Bush vowed to “end racial profiling” — were soon eclipsed by the expansion of police powers in the Patriot Act that responded to the terrorist attacks of Sept. 11, 2001.

Throughout the nation and especially in low-income areas, the divide that the Kerner Commission described persists, and issues of poverty and race are far less present in national political campaigns and media discussions today than they were four decades ago.

Instead of discussions about what might be done to diminish the likelihood of racial violence, the popular debate focused over the past week on how big the explosion of anger would be. In recent days, it was easy to find at least a dozen online polls asking something along the lines of, “Will there be race riots in Ferguson?”

On the left and right alike, there are complaints that the quick round of tsk-tsking that followed the August shooting did not equate to taking seriously the deep sense of injustice and inequality that pervades not only African American communities, but many other parts of the nation as well.

“We have made a national assumption that some black people, disappointed with the grand jury’s decision, will react with violence and mayhem,” wrote Bob Lonsberry on the conservative Free Republic site. That “deeply troubling” assumption “puts some black people in a unique category of people who have opted out of the social contract. That should bother us. . . . America does not trust black people to respond to a legal decision peacefully, and that is the result of either a horrific stereotype about black people, or horrific conduct by black people. Either way, we’ve got a problem.”

On the left, the discord in Ferguson has been viewed by some as part of a larger fraying of American society, of a piece with the “party riots” that have turned Mardi Gras, celebrations of sports teams’ defeats (and even some victories), and college drinking festivals into scenes of violent confrontation with police.

“Can’t you see it’s we who own the night?” sings, of all pop figures, Miley Cyrus, and often these days, it’s white college kids — drunk more on cheap hooch than on revolutionary rhetoric — who face off against the authorities. Some leftist theorists see social rebellion in such street battles, an uprising against the ocean of student debt, the paucity of jobs, the growing sense that the American promise of social mobility has been broken.

Such riots are an expression of “the exuberant togetherness of crowds and a sense of postgraduate precariousness,” writes Willie Osterweil, an essayist and punk musician, in the New Inquiry.

What those bursts of violence have in common with the eruptions that follow police shootings of young black men is a new sense of accountability driven by the ubiquity of smartphones and social media. Well after the fires burned out in Ferguson last summer, confrontations persisted between police and those who would train their phones’ cameras at the officers.

If Monday night’s violence was in part driven by the speed and ubiquity of the new media culture, that same new technology could be the basis for a far more palpable kind of change than study commissions or task forces have produced in the past. In earlier decades, arguments over police shootings would consist of debate between the official police version and the word of a witness or two with a different account. Now, the entire nation can see the shooting, the aftermath, the investigation — Brown’s body laying in the street, construction workers gasping in horror after the shooting, every twist and turn in the presentations to the grand jury. A mother’s grief gets played on an endless loop and so does a cop’s defense.

The omnipresence of video in this surveillance society creates both a new accountability for police officers — one that many departments now welcome, equipping their officers with body cameras — and a potentially real shift in power on the streets.