ATLANTA (AP) — The daughter of the slain civil rights leader the Rev. Martin Luther King Jr. exhorted the nation on King’s federal holiday to act out against injustice but to heed her father’s message of nonviolence.

The call Monday came amid a day of scattered protests over recent police deaths of unarmed black men that have shaken the U.S.

The Rev. Bernice King told those crowded into Ebenezer Baptist Church in downtown Atlanta, King’s spiritual home, much has been done to end injustice but much remains to fulfill her father’s dream.

“I challenge you to work with us as we help this nation choose nonviolence,” Bernice King told those gathered Monday at the main King tribute in Atlanta, where she urged a new generation to take up the courage and activism exhibited by those who struggled to oppose racial discrimination half a century ago.

This year’s annual holiday followed recent national protests and debate over the deaths of unarmed black men and youths at the hands of white police officers around the country.

Some new protests flared Monday such as one in which several dozen demonstrators blocked traffic on a march in Cleveland, Ohio. Dozens of other protesters were detained after blocking a bridge in San Mateo, California, authorities said. Protests also were reported in Missouri and Washington state amid tributes, speeches and volunteer service events around the nation in communities large and small.

“We cannot act unless we understand what Dr. King taught us. He taught us that we still have a choice to make: nonviolent coexistence or violent co-annihilation,” King’s daughter said as she made reference to the high-profile deaths.

“I cannot help but remember many women and men who have been gunned down, not by a bad police force but by some bad actors in a police force,” she said.

Protesters in California, many of them students at Stanford University, blocked the San Mateo-Hayward Bridge forcing westbound lanes to close for more than an hour Monday night, authorities said. The California Highway Patrol said numerous protesters were in custody and dozens could be seen being loaded into vans and taken off the bridge.

Elsewhere, the Northeast Ohio Media Group reported about 60 people gathered Monday at a recreation center where a Cleveland police officer fatally shot a 12-year-old. Their march ended at the city’s public square and police told the group some arrests were made.

In Seattle, authorities reported a handful of arrests after dozens of protesters chanting “black lives matter” disrupted traffic in Seattle on Monday.

The deaths have sparked a nationwide debate over police use of force, further fueled after two New York City police officers were shot to death last month by a man who suggested in online posts that he was retaliating for deaths in Ferguson, Missouri, and New York. The gunman, who was black, committed suicide.

New York’s mayor called Monday for his citizens to work together to ease the tensions.

“We will move forward as a city. We will move forward to deeper respect for all,” New York Mayor Bill de Blasio vowed at the city’s main MLK Day event in Brooklyn.

Elsewhere, The St. Louis Post-Dispatch reported two dozen protesters interrupted a King event at Harris-Stowe State University in that area, leading to angry confrontations with students outside a campus auditorium. Police kept watch, but no arrests were reported.

President Barack Obama, the nation’s first black president, sought to focus on encouraging a new generation to engage in service to others. In Washington, Obama and his wife Michelle went with one of their daughters, Malia, to a site for the Boys and Girls Clubs of Greater Washington to paint murals and assemble “literacy kits” of flashcards and books to help boost youth reading and writing skills.

In Philadelphia, activists pressed for several social justice causes under the King mantle, saying they wanted better police accountability, more education funding and a higher minimum wage.

In Atlanta, meanwhile, there were those who looked back at King and his legacy, some too young to have ever known him and some who marched by King’s side.

Actor David Oyelowo, who played kind in the movie “Selma” about a chapter of the civil rights era in which protesters were beaten and tear-gassed in 1960s Alabama, said at the Atlanta commemoration that playing King was a heavy burden.

The actor cried as he talked about putting himself in King’s place. “I only stepped into his shoes for a moment, but I asked myself, ‘How did he do it?'” Oyelowo said.

U.S. Rep. John Lewis told the Atlanta crowd he was just 17 when King sent him a bus ticket to head to Alabama to join the civil rights movement. Lewis marched alongside King and called him a hero who is “still a guiding light in my life.”

“The memory of such a great man can never, ever fade,” Lewis said. “I still think about him almost every day.”