The Missouri state trooper in charge of directing the law enforcement response to protests that have rocked a St. Louis suburb slammed "violent agitators" who he said were using largely peaceful protests as "cover" to commit criminal acts.

Missouri Highway Patrol Capt. Ron Johnson told reporters in Ferguson early Tuesday that 31 people had been arrested during a night of unrest that followed a day of largely peaceful protest. As Johnson spoke, two handguns and a Molotov cocktail that he said had been confiscated during the night by authorities lay on a table in front of him.

The majority-black town of approximately 21,000 has been roiled by unrest since the death of 18-year-old Michael Brown, who was fatally shot by a white police officer following a confrontation of some kind on the afternoon of August 9. Local authorities have fired tear gas and smoke canisters on an almost daily basis at protesters upset with the response to the shootings by Ferguson Police.

A visibly angry Johnson said that officers had come under heavy gunfire from protesters and at least two people had been shot. Johnson said he did not know the condition of the shooting victims. Four officers had been injured when they were struck by rocks or bottles, though Johnson claimed that police had not fired a single shot.

Citing what he called a "dangerous dynamic in the night," Johnson requested that protests take place during the daylight hours, so that officers could effectively isolate any troublemakers. However, Johnson said that his forces could not make protesters leave the streets after sunset if they did not want to.

"This nation is watching each and every one of us," said Johnson. "I am not going to let the criminals that have come here from across this country, or live in this neighborhood, define this community." Johnson added that some of those who had been arrested overnight had come from as far afield as New York and California. The trooper also directed his wrath at the assembled media, saying that they had put themselves and officers in danger by failing to clear areas when asked before imploring them to "not glamorize the acts of criminals."

"We do not want to lose another life in this community," Johnson added.

Shortly before midnight local time, the St. Louis Post-Dispatch reported that police fired tear gas at a group of protesters who had reportedly defied orders to leave the parking lot of a burned-out QuikTrip convenience store that has been near the center of demonstrations over the past eight day. St. Louis County Police Chief Sam Dotson told reporters that shots had been fired in the area and media members were told to go to a designated area about a quarter of a mile away.

Late Monday, reporters estimated that the number of protesters had dropped to around 100, far fewer than the number of media members who were covering them.

A photographer for the Getty photo agency was arrested while covering the demonstrations and later released. Two German reporters were arrested and detained for three hours. Conservative German daily Die Welt said correspondent Ansgar Graw and reporter Frank Herrmann, who writes for German regional papers, were arrested after allegedly failing to follow police instructions to vacate an empty street. They said they followed police orders.

At his news conference, Johnson said in some cases it was not immediately clear who was a reporter but that once it was established, police acted properly.

As darkness fell, National Guard units with armored vehicles were waiting at a staging area about a half-mile from the portion of West Florissant Avenue that has been the scene of the largest protests. Closer to the protest site, a crowd of demonstrators was marching and growing in size. Sheriff's deputies in body armor and state troopers carrying wooden bats and gas masks stood watch over the group.

The Post-Dispatch reported that some protesters began throwing bottles at police shortly after 10 p.m. local time. Authorities responded by ordering protesters to clear the streets and firing high-pitched sound cannons.

Another group of protesters marched toward the police lines and stopped, defying orders that demonstrators could not assemble in a single spot, but had to keep moving instead. The Post-Dispatch reported that an armored vehicle moved down the street trying to clear the crowd and a group of pastors locked arms and helped to move protesters away from the police line.

In federal court earlier Monday, a judge denied a request from the American Civil Liberties Union for a restraining order that would have prevented authorities from enforcing the no-stopping rule.

A grand jury could begin hearing evidence Wednesday to determine whether the officer, Darren Wilson, should be charged in Brown's death, said Ed Magee, spokesman for St. Louis County's prosecuting attorney.

The St. Louis County medical examiner's autopsy found that Brown was shot six to eight times in the head and chest, office administrator Suzanne McCune said Monday. But she declined further comment, saying the full findings were not expected for about two weeks.

Lawyers for Brown's family and hired pathologists said an independent autopsy determined that Brown was shot six times, including twice in the head.

Forensic pathologist Shawn Parcells, who assisted former New York City chief medical examiner Dr. Michael Baden during the private autopsy, said a bullet grazed Brown's right arm. He said the wound indicates Brown may have had his back to the shooter, or he could have been facing the shooter with his hands above his head or in a defensive position across his chest or face.

"We don't know," Parcells said. "We still have to look at the other (elements) of this investigation before we start piecing things together."

A third and final autopsy was performed Monday for the Justice Department by one of the military's most experienced medical examiners, Attorney General Eric Holder said. Holder was scheduled to travel to Ferguson later this week to meet with FBI and other officials carrying out an independent federal investigation into Brown's death.

Due to the unrest, the Ferguson-Florissant School District announced late Monday that classes would be canceled for the remainder of the week. Students were due to return from summer vacation last week, but were held out due to the unrest.

The Associated Press contributed to this report.

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