ATLANTA - The shootings in Arizona loomed large as the nation marked the legacy of the Rev. Martin Luther King Jr. on Monday, with many speakers drawing on his message of nonviolence as a key lesson in the wake of the tragedy.

National and local politicians joined members of the King family on Monday at his former church in Atlanta to mark what would have been the civil rights icon's 82nd birthday. It was also the 25th anniversary of the federal holiday established to honor King, who won the 1964 Nobel Peace Prize.

Attorney General Eric Holder told the audience at Ebenezer Baptist Church that the rampage in Tucson that killed six and seriously wounded Congresswoman Gabrielle Giffords is a reminder that King's struggle to promote peace continues.

Rep. John Lewis of Georgia, who worked with King during the civil rights movement, issued a renewed call for Americans to unite in peace and love as King preached during his lifetime.

King's son Martin Luther King III, the president and chief executive officer of The King Center, was to deliver the keynote address at the annual holiday observance at the church where his father preached from 1960 until his death in 1968.

Members of the King family also planned to lay a wreath at the tombs of Martin Luther King Jr. and his widow, Coretta Scott King.

King is the only American who was not a U.S. president to have a federal holiday named in his honor. He has been recognized on the third Monday in January since 1986.

The commemorative service caps a week of events that included a ceremony honoring King at the state Capitol and The Salute to Greatness Awards Dinner, which honored the late Sen. Edward Kennedy for his work on civil rights. His widow, Victoria, attended the ceremony and accepted the award on his behalf. The senator died at age 77 in 2009 after a battle with brain cancer.