A string of protests that began peacefully in Atlanta on Tuesday turned tense by nightfall.

Police and groups upset by the controversial grand jury decision Monday evening not to indict a white police officer in the August shooting death of an unarmed African-American teenager in Ferguson, Mo. squared off downtown with reports of vandalism and at about two dozen arrests right before midnight.

Protesters stirred by the decision took to the streets starting at noon with peaceful assemblies. By 9 p.m. the protests become confrontational, first with protesters blocking traffic on the Downtown Connector and later with storefront windows smashed.

The Atlanta protests mirrored others across the country where protesters blocked major traffic arteries.

Atlanta Police Department Chief George Turner counted 21 arrests at about 11 p.m.

“That number could change as we move through the night,” he said of the number of arrests.

Protesters broke a window at Meehan’s Public House on Peachtree Street and at a Wells Fargo Bank branch, they damaged an Atlanta Police Department vehicle and a taxi cab, and attempted to break a window at the Ellis Hotel on Peachtree, Turner said.

“I believe we are better than what we’re seeing,” Turner said. “Our plans for the rest of the night are to be here and to make sure our city is safe. We will not leave our city unprotected.”

The day began with calm, organized protest and the expectation that it would remain that way.

Shortly after noon, several hundred protesters raised a fist in the air and remained silent for 4 1/2 minutes — to commemorate the 4 1/2 hours that 18-year-old Michael Brown laid dead before authorities moved his body. The officer, Darren Wilson, told grand jurors he was defending himself. They were Atlanta University Center students who marched downtown and ended in front of CNN’s headquarters in downtown Atlanta.

Some demonstrators demanded to hear more from elected officials like Georgia Gov. Nathan Deal, Atlanta Mayor Kasim Reed and members of the state’s congressional delegation about measures they would take to reduce future concerns about potential police misconduct.

“Government officials need to speak up,” said Anthony Hegler, 28, a Kennesaw State University political science student who heard about the protest on social media and came downtown. “We need to make sure things are being done to prevent another black man from being killed.”

Hegler, a former U.S. Army veteran who said he served in Iraq and Afghanistan, said the changes should include video cameras on police officers and changes to the grand jury system to make the selection process more transparent.

Reed posted comments on Facebook encouraging the U.S. Justice Department to complete a thorough investigation of the shooting, which is ongoing. The mayor urged those angry with the grand jury’s decision to abide by the Brown family’s request to protest peacefully.

Initially, metro Atlanta seemed to heed the Brown family’s call. Regional law enforcement leaders met with community leaders in the days before the grand jury announcement to discuss potential protests and how to keep them non-violent.

Atlanta Deputy Police Chief C.J. Davis said at an afternoon news briefing there had been no incidents in Atlanta related to Monday night’s Ferguson decision. Neither did she expect any.

“We have had no indication that we will have any types of concerns today,” Davis said.

About 100 students gathered for the first major demonstration around midday Tuesday at Clark Atlanta University. Student leaders were joined by Atlanta City Councilmen Ceasar Mitchell and Michael Julian Bond, both AUC graduates, for the 90-minute session of speeches and prayer.

“The outcome of the case brought some things like police brutality into the dialogue, and it shows that these are issues that people have been thinking about,” said Faron Manuel, 22, Clark Atlanta’s student government president. “These problems have been there. They’re not new.”

Longtime CAU adjunct professor and civil rights leader Georgianne Thomas delivered one of the most emotional speeches of the rally, recounting her work in the Civil Rights Movement during the 1960s.

“What are we doing back here again?” Thomas asked while fighting through tears.

She ended her remarks with a verse of the Civil Rights standard, “We Shall Overcome.”

A few hours later, about 500 AUC students gathered at the Martin Luther King Jr. statue on Morehouse College’s campus. The students linked arms around the statue and sang before the march. Along the way, they chanted familiar civil rights slogans such as “Fired up! Ready to go” and newer calls, such as “Hands up. Don’t shoot!” Some witnesses in Ferguson said Brown had his hands in the air before he was fatally wounded.

Atlanta police drove alongside the students. Some motorists, temporarily stopped by police as the demonstrators marched, took pictures on their cell phones of the students. At CNN, where the march ended, some tourists looked on with curiosity. A few onlookers cheered the students on.

Some demonstrators in other parts of Atlanta voiced their concerns about the questionable deaths of some young, black men with Georgia ties. A couple mentioned Kendrick Johnson, the 17-year-old South Georgia high school student found dead in a rolled-up mat in the Lowndes High School gymnasium in January 2013. His death was ruled accidental.

In Savannah, where a grand jury is to consider whether to charge police in the fatal shooting of a handcuffed African-American suspect, authorities reported no unrest.

“We’ve already protested in August on Bay Street,” said Maurice Nelson, the president of the NAACP’s student chapter at Savannah State University. “Now, it’s more important to look at changing the laws and educating our community.”

Meanwhile, some prepared for another form of protest against the decision on Friday. A “blackout” to encourage African-Americans to buy only from black-owned businesses on Black Friday, the biggest shopping day of the year.

As the day wore on, the speeches by some protest leaders in Atlanta grew more antagonistic toward the police, who kept watch in silence.

“We have promised for four months f that if they gave us no justice we would give them no peace” screamed one speaker at a late afternoon rally at Underground Atlanta.

A few questioned the commitment of the demonstrators. Josh Ferrell attended the Underground Atlanta rally as a form of protest.

“I’m not here to support this,” said the 21-year-old Georgia State university graduate. “This is a form of regression. People go strong for a week then they’re back on the Internet talking about what they want for Christmas.”

As Ferrell watched, a speaker screamed, “No justice. No Peace,” a phrase firmly entrenched in modern black protest.

“This just promotes more violence,” Ferrell said. “Why say ‘no justice. No peace?’ You want peace.”

The crowd at Underground dwindled as the sun set. Many in the crowd chatted among themselves.

By nightfall, things took a different turn.