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David Goldman, Associated Press
A member of the color guard stands with an American flag before entering the Rev. Martin Luther King Jr. Day commemorative service at the Ebenezer Baptist Church, where King preached, Monday, Jan. 19, 2015, in Atlanta.

ATLANTA — Speakers honoring the Rev. Martin Luther King Jr. Monday at his spiritual home in Atlanta repeated the same message: We've come a long way, but there's still a lot left to be done to fulfill King's dream.

King's daughter, the Rev. Bernice King, urged those gathered at Ebenezer Baptist Church in Atlanta for the 47th annual Martin Luther King Jr. Annual Commemorative Service to act out against injustice. But she also said they should remember his message of nonviolence.

"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," she said. "I challenge you to work with us as we help this nation choose nonviolence."

The courage and sacrifice of those who participated in the civil rights movement of the 1950s and 1960s provides a model for those who want to act to effect change today, Bernice King said.

"We praise God for a new generation of activists," she said.

President Barack Obama and his wife, Michelle, also focused Monday on the next generation. Along with their daughter, Malia, they went to a District of Columbia site for the Boys and Girls Clubs of Greater Washington, where they helped paint murals and assemble "literacy kits" of flashcards and books to help youngsters improve their reading and writing skills.

Commemorative events and service projects were organized around the country to celebrate King's life and legacy. In cities nationwide, demonstrators also used the occasion to protest persistent inequality.

This year's King holiday follows several high-profile incidents in which unarmed black men were killed by police. Bernice King invoked the deaths of Michael Brown in Ferguson, Missouri, and Eric Garner in New York City and the fatal shooting of 12-year-old Tamir Rice in Cleveland, Ohio.

"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.

Those deaths sparked protests and debate over police use of force. The tensions grew 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 the deaths Brown and Garner. The gunman, who was black, committed suicide.

Speaking at a breakfast honoring King in Wilmington, Delaware, Vice President Joe Biden said minority communities and police departments need to work together to build relationships of trust.

"Do we see each other?" Biden asked. "Do we see each other for who we are?"

"We look at the yellow crime scene tape that is wrapped around America right now," said Alabama State University President Gwendolyn Boyd, delivering the keynote address at Ebenezer Baptist. "We know we still have a lot of work to do."

Boyd, who repeatedly brought the crowd to its feet with roars of applause, gave numerous examples to illustrate the changes since King's death, including the election of Obama, the country's first black president. But she also said now is not the time to rest or to be quiet, urging people to continue to strive to make a difference.

A day after he joined other actors from the movie "Selma" and hundreds of others in Alabama for a march to Selma's Edmund Pettus Bridge, where civil rights protesters were beaten and tear-gassed in 1965, actor David Oyelowo said during the commemoration in Atlanta that playing King was a heavy burden to bear. He 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. He explained that he, like King, has four children and said he cannot imagine walking through life knowing there were people who wanted to take their lives.

Oyelowo spoke of his family's Nigerian heritage, mentioning tribal scars still visible on the body of his father, who flew in from the United Kingdom for the service.

He said the legacy of slavery and the scars that it left are real but that they must not be allowed to define current generations. He noted that Hollywood too often casts minority actors as broken and subservient characters.

"I stand before you as a man who has played a king," he said defiantly.

Mathilde Mukantabana, Rwandan ambassador to the U.S., said in Atlanta that her country, which was torn apart by violence and genocide, serves as a shining example of the power of King's message.

"Martin Luther King's philosophy became our roadmap to reconciliation and peace," she said.

U.S. Rep. John Lewis, who told the crowd he was just 17 when King sent him a bus ticket to come to Montgomery to join the civil rights movement and who marched alongside King in Selma, recalled the man he called his hero and his leader, a man 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."

Associated Press writers Darlene Superville in Washington and Randall Chase in Wilmington, Delaware, contributed to this report.