But few are expecting peace as this St. Louis suburb prepares for a grand jury decision, expected in the next few weeks, on whether to indict the police officer who fatally shot an unarmed black man in August, inciting months of protests and putting Ferguson at the center of a national debate over the police and race.

Here, where heavily fortified police officers faced the demonstrators and the nights sometimes turned violent, even those shopkeepers who put in new windows are boarding up again.

“I hate this,” said Dan McMullen, the president of Solo Insurance Services, as he sat behind his desk on Thursday. During the course of a 20-minute conversation, his phone did not ring; no customers walked through the door. “Business is terrible,” he lamented. “The customers don’t want to come here anymore. We all know the grand jury is going to come back in the next couple of weeks, and everyone knows there won’t be an indictment. This time around will be a lot more violent.”

What Happened in Ferguson?

Why did the police shoot an unarmed black teenager in a St. Louis suburb, and what has unfolded since then? Here’s what you need to know about the situation in Missouri.

Mr. McMullen, a former police officer who is white, opened his desk drawer to show the loaded revolver that he keeps there.

“I don’t anticipate having to use it,” he said, but added that he was prepared to do so if necessary to defend his business.

All around this small suburb, people are bracing for the grand jury’s decision, with the wide expectation that the officer, Darren Wilson, will not face serious charges for shooting 18-year-old Michael Brown six times.

Government officials have said that forensics tests showed Mr. Brown’s blood on Officer Wilson’s gun, giving credence to the officer’s account that at one point he was pinned in his vehicle and engaged in a struggle over his gun with Mr. Brown. He told investigators that he had feared for his life, and police officers are typically given wide latitude to defend themselves if they feel their safety is threatened.

Nor are civil rights charges expected. Federal officials have said that while their investigation is continuing, the evidence so far does not support such a case against Officer Wilson.

But people protesting police tactics, who have continued to hold marches here since the shooting on Aug. 9, say they envision larger, angrier demonstrations should Officer Wilson not be charged. Fearing renewed unrest, the police in the region have bought new riot gear, called meetings with nearby departments and held special training seminars.

School leaders are reviewing emergency contingency plans and urging officials to announce the grand jury finding outside of school hours — perhaps on a Sunday, so that children returning home are not caught in a melee.

Behind the scenes, government officials at various levels have been struggling with how to orchestrate and blunt the effects of the grand jury announcement. Investigators in Missouri want the Justice Department to announce the results of its civil rights investigation at the same time, according to several people briefed on the case, who insisted on anonymity to discuss confidential conversations. Yet Justice Department officials, who have promised that their investigation will be independent, do not want to coordinate announcements.

Other government officials have been privately discussing whether they can pressure the Ferguson police chief, Thomas Jackson, to step down, or somehow substitute the St. Louis County police for the local force. The county prosecutor, Robert P. McCulloch, has said that if the grand jury does not indict Officer Wilson, he will take the unusual step of releasing the evidence for public scrutiny if a judge approves.

 Mr. Brown’s parents are preparing to call on the people of Ferguson not to react violently to the grand jury’s decision, even though they have little faith in the prosecutor, according to their lawyer, Benjamin L. Crump. “We want people to pray that the system will work, but the family doesn’t have much confidence at all,” Mr. Crump said. Nor, he added, are they confident that the local police will deal properly even with peaceful protesters.

Regardless of what the grand jury decides, Mr. Crump said the Browns would dedicate themselves to pressuring the federal government and states to pass “Michael Brown laws” that would require officers to wear video cameras.

“The real change they want is for people to use their frustration and turn it into legislation,” he said. “If you get the Mike Brown law passed, nobody will have to deal with something like this and the insult to injury afterwards.”

Some protest groups have said that they are urging demonstrators to be peaceful. The Don’t Shoot Coalition, which formed in the aftermath of the shooting, is pressing local officials for coordination in advance of the grand jury’s return so that members can adequately prepare for the announcement. The coalition, which represents about 50 groups, said this week that it was promoting “a peaceful response” from demonstrators.

Elected officials have tried to soothe nerves in recent days, even as some police departments have bought more pepper-spray balls, flexible handcuffs and batons, and, in the case of at least one department, decided to delay repairing police vehicles until any unrest is over. Anxious business owners filled part of a banquet hall here the other night, brimming with worries.

At the meeting, billed as a “disaster preparedness seminar,” they peppered city officials with questions: If Officer Wilson faces no charges, will Ferguson be able to manage the ensuing protests? Should they be stocking up on fire extinguishers, in case someone tries to burn down their stores? Should they arm themselves? Yon Kim, a clerk at a beauty supply store, later described the growing tension. “I know it’s not going to be smooth,” she said. “The customers are already scared. And if something happens, we don’t know if insurance is going to cover it.”

“There’s going to be protests,” Lt. Col. Al Eickhoff, an assistant Ferguson police chief, told the business owners, while urging them to be careful how they respond. “Once you pull that trigger,” he warned, “you cannot pull that bullet back.”

Among the other bits of less-than-reassuring guidance for business owners: Empty your trash often, fire officials said, so it is not set aflame during protests. And Mayor James Knowles III suggested that people steer clear of the area in the evening if protests break out. “By 8, 9 o’clock, nothing good is going to happen out on the streets,” Mr. Knowles said. “When the gremlins come out, you’re just going to get caught in the crossfire.”

And the protests go on. Nearly every night, demonstrators gather in front of Police Headquarters on South Florissant Road, chanting and confronting police officers with expletive-laden cries and promises to shut the streets down.

On Wednesday evening, an unusually large crowd of more than 100 protesters was there, many with garish Guy Fawkes masks of white faces. The police, wearing riot gear and armed with plastic handcuffs, warned the protesters that if they continued to block the road, they would be arrested. The group defied the police, marching down the middle of the street and leaving a traffic jam behind them. Some pounded on cars whose drivers were trying to maneuver through. One driver, a white-haired older woman, turned onto South Florissant, saw the protesters and did a hasty U-turn to avoid being trapped by the crowd.

At times, officers appeared to struggle to remain calm in the face of insults. “You’re three-fifths of a person,” one woman taunted a black police officer, who turned his back and walked in the opposite direction.

The leaders of at least three police departments — the Missouri State Highway Patrol, the St. Louis County Police Department and the St. Louis Police Department — have held regular meetings as part of an effort at unified preparation. “We’re focused on the preservation of life and property,” Jon Belmar, the chief of the county police, said in an interview. His department spent $37,741 in October on helmets, shields, batons and shin guards.

A central goal, some law enforcement officials said, is to ensure that peaceful demonstrators are able to voice their views while also preventing violence.

The St. Louis Police Department has spent $325,000 on new equipment, including riot gear; sent 350 officers to training sessions on how to manage civil disobedience; and met with police chiefs from other communities around the nation that have dealt with unrest. Still under consideration are canceled days off for officers and 12-hour shifts. “We’ll be prepared to respond,” said D. Samuel Dotson III, the chief in St. Louis.

Capt. Ronald S. Johnson, the Missouri State Highway Patrol official who became the public face of law enforcement here after early clashes, said he had spoken to school groups and church panels about long-term changes needed in Ferguson. Still, the grand jury’s looming decision comes up regularly.

“I tell them that we’re going to make it through whatever happens,” Captain Johnson said in an interview. “I also tell them that it is my belief that whatever happens is not going to be as bad as we believe it’s going to be. I also tell them that I believe we’ll be better for it. But I tell them that I look at each day for each day.”