Larry Copeland, Kevin Johnson and John Bacon

USA TODAY

FERGUSON, Mo. — St. Louis County prosecutors plan to begin presenting evidence Wednesday to a local grand jury as part of an investigation into the fatal shooting of Michael Brown, a spokesman said Tuesday.

Edward Magee, spokesman for St. Louis County Prosecuting Attorney Robert McCulloch, said local investigators have interviewed Ferguson police Officer Darren Wilson and he will be "offered the opportunity'' to testify if he chooses.

Magee said the case will be presented to a regular grand jury that already has been seated. He said the panel has a few weeks remaining in its current term. He did not know how long it would take to present the case.

"We will extend the term, if necessary,'' Magee said.

A federal inquiry is also underway.

Attorney General Eric Holder on Tuesday promised a "fair and thorough'' investigation into the fatal shooting of Brown, an 18-year-old African American, in an op-ed for the St. Louis Post-Dispatch in advance of his trip to Ferguson on Wednesday.

"Since the Aug. 9 shooting death of Michael Brown, the nation and the world have witnessed the unrest that has gripped Ferguson, Mo,'' Holder wrote. "At the core of these demonstrations is a demand for answers about the circumstances of this young man's death and a broader concern about the state of our criminal justice system.''

Holder said he was traveling to the city to be briefed on the federal civil rights inquiry. He said "hundreds" of potential witnesses have been interviewed, He cautioned that the inquiry will "take time to complete."

"At a time when so much may seem uncertain, the people of Ferguson can have confidence that the Justice Department intends to learn — in a fair and thorough manner — exactly what happened,'' Holder wrote.

"Approximately 40 FBI agents and some of the Civil Rights Division's most experienced prosecutors have been deployed to lead this process,'' the attorney general said, adding that the federal autopsy he called for over the weekend was completed Monday. As with the family's examination, additional investigation is needed to determine critical facts, including whether Brown was facing the officer when he was shot and the distance between Brown and the officer at the time of the shooting.

Holder said he hopes the federal investigation will bring a measure of calm to Ferguson. He called for "an end to the acts of violence." He also called on police to help reduce tensions and regain the community's trust.

Missouri State Attorney General Chris Koster visited West Florissant Avenue shortly after sunset Tuesday and announced to a group of protesters that a grand jury would be convening at 9 a.m. Wednesday CST.

"My understanding is that two senior prosecutors are going to bring the matter before a grand jury--one of whom is an African American woman," he said. "My prayers are with them that they do a great job."

Koster said he visited Ferguson because it is important for elected officials to "recognize the frustration that is being expressed and come out and interact and talk with people in the community." Koster said, "These folks are my bosses. I work for them."

Meanwhile, as another night began in Ferguson hundreds of protesters continued to demonstrate, many marching up and down West Florissant Avenue.

Things remained calm until just before midnight when a glass bottle was thrown at police. Police then ordered the protesters to disperse and rushed into the crowd in pursuit of a suspect.

One tense moment came when police forced protesters out of a parking lot. After initially resisting, the demonstrators moved back onto the sidewalks.

Police instructed protesters that they must keep the march moving and told those who did not wish to keep walking that they could rest in the media staging area.

"I'm not here for exercise," one protester yelled at police,

Local leaders issued a statement pleading for calm and promising changes in the police department as the city braced for another night of protests and possible confrontation.

"We plan to learn from this tragedy," city officials said in the statement. Officials are working to increase the number of black law enforcement applicants and raise funds for cameras for patrol car dashboards and officer vests, the statement said.

Ten days of protests and violence are taking their toll on this normally quiet St.Louis suburb of 21,000 people.

"This has to stop," Missouri State Highway Patrol Capt. Ron Johnson said Tuesday.

Johnson is tasked with bringing peace to a city torn apart by violence since Brown, 18, was shot by Wilson, 28, setting off angry protests that have made international headlines.

Brown's funeral will be Monday, family lawyer Benjamin Crump said.

Also Tuesday, a 23-year-old man was fatally shot by a police officer in north St. Louis, just a few miles from Ferguson. Authorities said he had threatened officers with a knife and implored them to kill him.

Dozens of people milled about Tuesday night the area where the man was shot, waving signs and chanting, "Hands up! Shoot back!"

There's a fairly heavy police contingent of about a dozen city police officers but they're staying in the background. At one point Tuesday evening, the proprietors of one of the businesses in the strip mall near the shooting drove up in a U-Haul truck, loaded up furniture, a television and other items from the business, and left.

The relative quiet in Ferguson Tuesday comes hours after peaceful demonstrations once again descended into chaos overnight. Police said they came "under heavy gunfire" and arrested 78 people.

Johnson said four police officers were injured by thrown rocks and bottles, at least two people were shot and two fires were set during another night of clashes between police and protesters that lasted into early Tuesday.

Johnson lauded local police, state troopers and National Guard personnel, saying they "acted with restraint and calm." He said police were shot at but did not fire any shots themselves.

"I don't want anyone to get hurt. I don't want an officer to get hurt, I don't want a citizen to get hurt. We have to find a way to stop it," he said.

Even in daylight hours, life has not returned to normal. The school year had been scheduled to begin more than a week ago, but Ferguson-Florissant district officials canceled classes last week because of the unrest. Then they canceled school again Monday and said they would try for next Monday.

"We believe that closing schools for the rest of this week will allow needed time for peace and stability to be restored to our community and allow families to plan ahead for the additional days that children will be out of school," school officials said in a written statement.

Businesses are hurting. Kathleen Osborn, executive director of the Regional Business Council in the St. Louis area, said about 25 businesses have been directly damaged by violence, many more simply by fear that is keeping many residents from leaving their homes.

"The tragedy of it is that we are talking about small businesses," she told USA TODAY. "Yet they are extraordinarily resilient. Some of these business owners get up in the morning, clean up their damage and open their stores. The problem is that you can't get them fully back in order until you know there won't be any more damage."

Many protesters realize the violence has to stop. Monday night, a group of people trying to keep the peace locked arms and positioned themselves between the more confrontational protesters and the police line. However, while many among the protesters clamored for calm, some in the crowd appeared determined to provoke an incident.

Johnson said some of those arrested were from as far as New York and California — part of what he called "a dangerous dynamic of the night."

Of 78 arrests, only four were Ferguson residents. Many were from the surrounding area. Eighteen were from out of state.

"Our peaceful protesters are not the enemy," Johnson said. "Tonight we closed the roadway. We allowed those who come in peace to walk the roadway."

Contributing: Yamiche Alcindor