Protests in St. Louis over a former police officer's acquittal in the shooting death of a black man continued Monday after a weekend capped by the arrests of more than 80 people.

About a hundred people marched silently through downtown on Monday, breaking into chants of "If we don't get it, shut it down!" at City Hall, the St. Louis Post-Dispatch newspaper reports. And St. Louis Public Radio reports that several students walked out of at least two area high schools in protest.

A day earlier, hundreds of peaceful protesters took to the streets, gathering at police headquarters and marching through city streets. But daylight demonstrations on Sunday were a different affair than what occurred once the sun set.

"The vast majority of protesters are nonviolent but for the third day in a row the days have been calm and the nights have been destructive," St. Louis Mayor Lyda Krewson said in a briefing, adding that "agitators" stayed behind, breaking windows and destroying property.

The Post-Dispatch reports that on Sunday:

"The vandalism began about 90 minutes after a leader of the protesters said the group had met its objective of bringing a large, diverse group of people out to peacefully assemble." 'We met our goal. We are dispersing,' said Pastor Doug Hollis about 6:30 p.m. 'This was a great, peaceful protest. That's what we want.' "

A Twitter user who goes by Rebelutionary Z and who has been live-streaming the protests said that late-night demonstrators on Sunday were boxed in by police and sprayed with a chemical agent "for no ... reason."

"We are completely trapped," he says near the end of a 45 minute-long video. The footage shows police in riot gear and officers with bicycles surrounding a group of protesters with shouts of "get on the ground" and spraying them with an unknown substance before handcuffing and hauling many of them away.

Also caught up in Sunday's arrests was Post-Dispatch reporter Mike Faulk. Just after midnight Monday, he tweeted: "Less than 100 of us including media blocked in at wa and Tucker all four sides. People moving toward bike cops looks like best option."

Authorities said they confiscated weapons. And The Associated Press reports that "according to police, the demonstrators then sprayed bottles with an unknown substance on officers." The news service says one officer suffered a leg injury and was hospitalized.

"The police own tonight," St. Louis interim Police Chief Larry O'Toole said after the arrests. "Some criminals assaulted law enforcement officers and threw chemicals and rocks at them."

The AP reports that some officers in riot gear were chanting "Whose street? Our street!"-- something commonly heard from protesters.

On Friday, former Officer Jason Stockley was acquitted of first-degree murder in the 2011 shooting death of Anthony Lamar Smith following a high-speed chase. Prosecutors had alleged that Stockley planted a gun in Smith's car. As The Two-Way noted, "The verdict over Smith's killing has been highly anticipated — and it prompted protests outside the courthouse."

The most recent protests are taking place not far from Ferguson, Mo., where the shooting death of 18-year-old Michael Brown by a white police officer in 2014 led to months of racially-charged unrest.

On Saturday, both U2 and Ed Sheeran called off weekend shows citing safety concerns after police said they could not provide sufficient protection.

"We have work to do here in the city," the St. Louis Mayor Krewson said. "We need more and better opportunities for all of our citizens, but destruction cannot be tolerated"

Protesters have promised weeks of demonstrations, according to St. Louis Public Radio.

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