BALTIMORE -- A line of police behind riot shields hurled tear gas canisters and fired pepper balls at as many as 200 protesters Tuesday night to enforce a citywide curfew, imposed after the worst outbreak of rioting in Baltimore since 1968.
Demonstrators threw bottles at police and picked up the canisters and hurled them back at officers.
But the crowd rapidly dispersed and was down to just a few dozen people within minutes.
The city's streets remained quiet overnight.
The confrontation came after a day of high tension but mostly peaceful protests, reports CBS News correspondent Jeff Pegues. There was even singing and dancing.
Thousands of police officers and National Guardsmen poured in to try to prevent another round of looting and arson like the one that rocked the city on Monday.
It was the first time since the assassination of the Rev. Martin Luther King Jr. in 1968 that the National Guard was called out in Baltimore to quell unrest.
Maryland Gov. Larry Hogan said 2,000 Guardsmen and 1,000 law officers would be in place overnight.
"This combined force will not tolerate violence or looting," he warned.
In a measure of how tense things were on Tuesday, Baltimore was under a 10 p.m.-to-5 a.m. curfew imposed by Mayor Stephanie Rawlings-Blake. It is expected to last a week.
All public schools were closed in Baltimore Tuesday. The Orioles postponed Tuesday night's game at Camden Yards and - in what may be a first in baseball's 145-year history - announced that Wednesday's game will be closed to the public.
The streets were largely calm all day and into the evening, with only a few scattered arrests.
The message was loud and clear in the moments leading up to the curfew, Pegues says.
Self-appointed peacekeepers pleaded with people to get off the streets.
Among them, Congressman Elijah Cummings and Vietnam veteran Robert Valentine.
"Y'all want to go home now, don't want to see you in trouble," Valentine said. " ... It's not worth it. You cannot prove anything with your anger. If you use your mind and do it pacify you can get further. Sit down to the table and talk."
A recorded message was blasted across the city, on the ground and in the sky, warning people to go home.
About 15 minutes after the 10 p.m. curfew took effect, police moved against protesters who remained in the street in the city's Penn North section, near where a CVS pharmacy was looted the day before.
Shortly before the curfew and in a different neighborhood, police arrested three to four juveniles in South Baltimore after people started attacking officers with rocks and bricks, authorities said. At least one officer was reported injured.
Baltimore Police Commissioner Anthony Batts told reporters late Tuesday the curfew seemed to be working.
He said only 10 people had been arrested following start of the curfew, including seven for violating the curfew. He said two people were arrested for looting and one for disorderly conduct.
Batts said he was pleased with the efforts of dozens of community organizers, clergy and neighborhood activists who urged residents to remain calm.
"The curfew is, in fact, working," Batts said. "Citizens are safe. The city is stable. We hope to maintain it that way."
Monday's outbreak of looting, arson and rock- and bottle-throwing by mostly black rioters erupted just hours after Gray's funeral.
It was the worst such violence in the U.S. since the unrest last year over the death of Michael Brown, the unarmed black 18-year-old shot by a white police officer in Ferguson, Missouri.
At the White House Tuesday, President Obama called the deaths of several black men around the country at the hands of police "a slow-rolling crisis." But he added that there was "no excuse" for the violence in Baltimore, and said the rioters should be treated as criminals.
"They aren't protesting. They aren't making a statement. They're stealing," the president said.
Political leaders and residents called the violence a tragedy for the city and lamented the damage done by the rioters to their own neighborhoods.
"I had officers come up to me and say, 'I was born and raised in this city. This makes me cry,"' Batts said.
Haywood McMorris, manager of the wrecked CVS store, said the destruction didn't make sense: "We work here, man. This is where we stand, and this is where people actually make a living."
But the rioting also brought out a sense of civic pride and responsibility in many Baltimore residents, with hundreds of volunteers turning out to sweep the streets of glass and other debris with brooms and trash bags donated by hardware stores.
"Now you're looking at burnt down store fronts, broken glass. It's senseless," Mira Keene told CBS Baltimore.
Twenty-four hours after the violence, a different message was spreading, the station said.
Tuesday night, dozens of protestors marched through the streets of West Baltimore, calling for peace in the city. "This is where we live at. They destroyed where we live," Tia Sexton told CBS Baltimore.
Blanca Tapahuasco brought her three sons, ages 2 to 8, from another part of the city to help clean up the brick-and-pavement courtyard outside the CVS.
"We're helping the neighborhood build back up," she said. "This is an encouragement to them to know the rest of the city is not just looking on and wondering what to do."
Some of the same neighborhoods that rose up this week burned for days after the assassination of the Rev. Martin Luther King Jr. 47 years ago. At least six people died then, and some neighborhoods still bear the scars.
Jascy Jones of Baltimore said the sight of National Guardsmen on the street gave her a "very eerie feeling."
"It brought a tear to my eye. Seeing it doesn't feel like the city that I love," she said. "I am glad they're here, but it's hard to watch."
The rioting started in West Baltimore on Monday afternoon and by midnight had spread to East Baltimore and neighborhoods close to downtown and near the baseball stadium.
At least 20 officers were hurt, one person was critically injured in a fire, more than 200 adults and 34 juveniles were arrested, and nearly 150 cars were burned, police said. The governor had no immediate estimate of the damage.
With the city bracing for more trouble, several colleges closed early Tuesday, including Loyola University Maryland, Johns Hopkins University and Towson University.
The violence set off soul-searching among community leaders and others, with some suggesting the unrest was about more than race or the police department - it was about high unemployment, high crime, poor housing, broken-down schools and lack of opportunity in Baltimore's inner-city neighborhoods.
The city of 622,000 is 63 percent black. The mayor, state's attorney, police chief and City Council president are black, as is 48 percent of the police force.
"You look around and see unemployment. Filling out job applications and being turned down because of where you live and your demographic. It's so much bigger than the police department," said Robert Stokes, 36, holding a broom and a dustpan on a corner where some of the looting and vandalism took place.
He added: "This place is a powder keg waiting to explode."
In the aftermath of the riots, state and local authorities found themselves facing questions about whether they let things spin out of control.
Batts, the police commissioner, said police did not move in faster because those involved in the early stages were just "kids" - teenagers who had just been let out of school.
"Do you want people using force on 14- 15- and 16-year-old kids that are out there?" he asked. "They're old enough to know better. But they're still kids. And so we had to take that into account while we were out there."
Mayor Stephanie Rawlings-Blake waited hours to ask the governor to declare a state of emergency, and the governor hinted she should have come to him earlier.
"We were trying to get in touch with the mayor for quite some time," Hogan said. "She finally made that call, and we immediately took action."
Rawlings-Blake said officials initially thought they had the unrest under control.
Gray was arrested April 12 after running away at the sight of police, authorities said. He was held down, handcuffed and loaded into a police van. Leg cuffs were put on him when he became irate inside. He died a week later.
Authorities said they are still investigating how and when he suffered the spinal injury - during the arrest or while he was in the van, where authorities say he was riding without being belted in, a violation of department policy.
Six officers have been suspended with pay in the meantime.