WASHINGTON (CNN) -- Demonstrators protesting police violence laid down in the street several blocks from the White House on Monday, blocking rush hour traffic.
Protesters chanted, "black lives matter" and "off the sidewalks, into the streets."
One woman held a sign that said, "Stop killing us."
The demonstration blocked traffic at cross streets along Connecticut Avenue, a major thoroughfare that connects the White House to upper northwest Washington.
It was one of a number of national demonstrations planned for Monday night, days after a grand jury in New York City decided not to indict a police officer in Eric Garner's death and two weeks after a Missouri grand jury decided not to indict former Officer Darren Wilson in the killing of Michael Brown.
In New York City, police were bracing for more demonstrations Monday. Activists were threatening to disrupt the visit of the Duke and Duchess of Cambridge, who are scheduled to attend a Nets game in Brooklyn.
A large crowd of demonstrators had already gathered outside the Barclays Center on Monday evening before the game started. Inside the arena, several players showed support for protests, according to CNN partner Bleacher Report.
As they warmed up for the game, Cleveland Cavaliers LeBron James and Kyrie Irving were among the players wearing T-shirts that said "I can't breathe" -- Garner's last words, which have become a rallying cry for protesters.
Brooklyn Borough President Eric Adams said officials there are prepared for protests.
"There's nothing more American than having the right to voice your concern," he said. "We want them to be constructive and not destructive. What we saw in St. Louis, we don't want in the borough of Brooklyn."
New York mayor praises police
New York Mayor Bill de Blasio praised police officers' handling of the protests.
"They've respected people's right under the First Amendment to express their views. They've kept the peace. They've kept order," he told reporters Monday. "We had only a handful arrests the last two days, which is extraordinarily impressive given all of the activity that's happening."
De Blasio says he understands parents who are worried about what might happen if their kids encounter police. The New York mayor says he's had to warn his own son about that possibility.
"When he was just becoming a teenager, you know, the conversation was a difficult one and a complicated one, because you're trying to say to a young person who obviously looks up to police, you know, be careful and be smart and respect the police, but also recognize that there are these realities to be grappled with -- and that's a tough conversation to have with a young man," he said.
De Blasio is white. His son is biracial.
"This is a national reality. It's not just a New York reality," de Blasio said. "And that, unfortunately, is further evidence of how much more we all have to learn from each other. ... The goal is to get to a day when no parent feels they have to have that conversation."
Protesters flood California highway
Protesters across the country demanded justice over the weekend for Garner, Brown and other black men who have died at the hands of police.
Demonstrators flooded a highway in Oakland, California, late Sunday night, prompting a heated standoff in the freeway between protesters and the California Highway Patrol.
Some threw explosives, bottles and rocks at officers, authorities said. Highway Patrol Sgt. Diana McDermott said it wasn't clear what type of explosives were thrown, but she said some in the crowd had Molotov cocktails and M-80 firecrackers.
Officers responded by deploying gas and arresting eight protesters. In the end, two officers suffered minor injuries.
Gurpreet Heer, a student at the nearby University of California, Berkeley, said he saw people throwing glass and rocks at police.
"People were vandalizing police cars and jumping on the cars," Heer said.
Police said five patrol cars were damaged.
In the city of Berkeley, protests spilled into Monday morning. Some protesters looted and vandalized businesses, police spokeswoman Jennifer Coats said.
One protester was struck in the head with a hammer when he tried to keep fellow protesters from damaging and looting a Radio Shack, she said. The man was hospitalized, but his injuries are not believed to be life-threatening.
Two Berkeley officers also suffered minor injuries. Coats said five people were arrested, but she did not know the charges.
The acts of violence were apparent anomalies in a sea of protests nationwide decrying a grand jury's decision not to indict the officer who killed Garner, an unarmed black man.
Caroling their grievances
Some demonstrators are getting more creative in delivering their message.
In New York, protesters at Penn Station sang "justice carols," such as these lyrics to the tune of "Little Drummer Boy":
"Help, he told them,
pa rum pum pum pum,
I cannot breathe, you see,
pa rum pum pum pum,
Our city's finest bring,
pa rum pum pum pum,
Death to this human being."
Hundreds of protesters also gathered at Grand Central Terminal and Macy's in Herald Square -- sites of multiple "die-ins" over the past few days -- before barging through the nearby Toys R Us to lie on the floor en masse.
One young couple made the event a family affair, lying on the floor with their toddler between them.
"What's happening in these cities in these last several days is incredibly important to show we have a unified voice," said Judi Flournoy, who was participating in a New York protest.
While protesters chanted "Black lives matter," many of the demonstrators were not black.
"They rarely shoot old white guys like me," one protester's sign read.
While some protesters in New York chanted, "How do spell racism? NYPD," members of the New York Police Department marched alongside them, showing restraint.
Not everyone is on their side
But in Imperial, Missouri, demonstrators staged a different kind of protest Sunday.
They burned St. Louis Rams football jerseys after five players ran onto the field last weekend making the "hands up, don't shoot" gesture, CNN affiliate KSDK reported.
That gesture became a symbolic part of anti-police demonstrations in the Michael Brown case.
"Why would you do something like that? It's utterly ridiculous," said Larry Magee. "I think the Rams ought to pack their bags, and I'll give them a plane ticket back to L.A."
Daughter: 'This is not a black-and-white issue'
Garner's daughter Erica said she was deeply moved by the diversity of protesters who have demonstrated across the country.
"This is not a black-and-white issue. This is a national crisis," Erica Garner said.
U.S. Attorney General Eric Holder has announced a federal civil rights investigation into Garner's death.
Unlike with the Michael Brown case, a video showing the moments leading up to Garner's death has been widely circulated.
Erica Garner says that video has struck a nerve with many.
"For white people to come out and show how deeply they was hurt and like Asians and, you know, different people from different nations and different parts of the world to come out and show that they felt the same way I felt on that video, I greatly appreciated it. It's like a sense of I'm not the only one that feels this way."