Thousands of people took to the streets of Boston Sunday in protests against police killings of black Americans. The events followed days of demonstrations across the country, some of which have ended in violence.

Sunday afternoon several hundred protesters marched downtown from City Hall to the Boston Common and then to Boylston Street, chanting "No justice, no peace," "black lives matter," and "silence is violence." There was a light police presence for most of the march and no signs of the violence that had erupted in other cities in recent days. Later in the evening, clashes between police and some people turned violent after the marchers dispersed.

Another protest began Sunday evening at Nubian Square with hundreds of people marching to the State House. As marchers moved up Washington street, dozens of police on bicycles lined the protest route.

South End resident Olivia Martin told WGBH News, "I was here when the riots started here back in the '60's. I've had different people I've loved, family and friends died from this. So what are we supposed to do, keep accepting it?"

Martin said she has lived in Boston 44 years.

"I came from Ku Klux Klan land, when it was alright to say that they hated us, but at least we knew who they were," she said. "And they weren't hiding behind three-piece suits."

"Things definitely feel different — it feels like much more of a tinderbox," said Rev. Liz Goodman, a United Church of Christ pastor from Lenox. "And I think the national rhetoric is really off the mark. I mean, I don't even know what to expect from the summer."

Sparked by the death of George Floyd — a black man who was killed when a white police officer pinned him under his knee in Minneapolis Monday — the demonstrations have rocked cities and towns throughout the U.S. in recent days, from New York to Los Angeles. Peaceful protests involving tens of thousands of people on Saturday gave way, in some places, to rioting, looting and violence, with police vehicles torched, stores emptied and objects hurled at officers. The police response varied from restrained to aggressive, with officers at times firing tear gas and rubber bullets.

People of all ages gathered for the protests on Sunday, including those who had recently finished high school and find themselves in a world more uncertain than usual.

Joseph Fede and Joshua Fontanez both just graduated from Cambridge Rindge and Latin School.

Fontanez said seeing the violence against black Americans "really does hurt."

"I'm hurting for them, for every black person," he said.

"I mean, it's hard 'cause a lot of things are stacking up on us, but we gotta stay strong and just keep fighting through it and make sure we win in the end," Fede added.

Preston Gordon marched holding a flag to honor his brother, who served as a cop and is currently deployed serving his fourth tour in the military. "Police brutality is just the tip of the iceberg," he said. "It's the system that's wrong."

As the march passed Tufts Medical Center, the protesters clapped, while emergency room staff looked on. Dr. Furman Walls, an emergency room physician, stood outside to watch. "You try to take care of people, and then you leave work and you realize your life is at risk for something you've never done," he said. "It's nice to know that people stand up and say no."

At the end of the march, organizers urged protesters disperse peacefully and encouraged activists to continue the movement. Tensions rose not long after, as some people began throwing frozen water bottles at the police and a cruiser was set on fire. Police in riot gear with batons began shutting down the streets.

"The time for protesting is over," the Boston Police Department tweeted. "The peaceful protest ended hours ago. Individuals now congregating in the area of Boston Common and Downtown Crossing need to vacate the area and go home."

Mayor Marty Walsh issued a statement congratulating the protesters on a peaceful day of demonstration, but added, "I am angered, however, by the people who came into our city and chose to engage in acts of destruction and violence, undermining their message."

The Associated Press contributed to this article.