ATLANTA - Saying the shooting in Arizona that killed six and seriously wounded Congresswoman Gabrielle Giffords underscores the need for the Rev Martin Luther King Jr's message, the civil rights leader's son was expected to address a crowd gathered Monday to mark the 25th anniversary of the federal holiday for his father.

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

He has linked the holiday honoring the winner of the 1964 Nobel Peace Prize winner to the shootings in Tucson, Ariz., which left six dead and Giffords fighting for her life.

King would have been 82 on Jan 15. Members of theKingfamilyalso 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 US 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. Also scheduled to speak Monday was US Attorney General Eric Holder.