President Obama Speaks At “Together We Thrive: Tucson And America"

More than 12,000 people at the University of Arizona's McKale Memorial Center and millions more across the country will hear President Obama talk about Saturday's shooting in Tucson, Ariz., that killed six and wounded 14, including Rep. Gabrielle Giffords. The president worked throughout the night on the speech, sources said, and was editing his text on Air Force One flying from Washington to Tucson this afternoon.

Click here for full ABC News' coverage of the tragedy in Tucson. Shortly after touching down in Arizona, the president and first lady headed to University Medical Center in Tucson to visit Giffords, D-Ariz., and her husband, space shuttle Capt. Mark Kelly, as well as other victims of Saturday's shooting.

""The president wanted to begin this solemn trip by stopping first at the hospital where Congresswoman Giffords and others contunue to recuperate,"" White House Press Secretary Robert Gibbs said.

The speech was expected to be short, perhaps 10 to 15 minutes, and part of a broader program that is expected to last about an hour, including music, moments of silence, prayers and other speeches.

One goal was to minister to those mourning and honor those impacted by the shootings -- including the victims, the heroes and those grieving in Tucson and beyond. Another goal was to lift up the nation in this moment, not sully it with politics.

What the president said -- and didn't say -- was expected to be closely watched. At its heart, the speech was expected to be about healing.

During times of national tragedy the president is called upon, formally and informally, to serve as a compass for the nation going forward, sorting though grief and bringing hope in the face of tragedy. "