"At a time when our discourse has become so sharply polarized," President Obama told the "Together We Thrive: Tucson and America" memorial service at the University of Arizona's McKale Memorial Center, "at a time when we are far too eager to lay the blame for all that ails the world at the feet of those who think differently than we do, it's important for us to pause for a moment and make sure that we are talking with each other in a way that heals, not a way that wounds."
Among the injured when a gunman opened fire at a "Congress on Your Corner" event for Rep. Gabrielle Giffords, D-Ariz., outside a supermarket Saturday morning in Tucson was Giffords herself. The congresswoman was shot a point blank range in the back of the head and has been in critical condition ever since.
Obama revealed during his speech that after he visited with her at the hospital earlier in the day, Giffords opened her eyes for the first time.
"Gabby opened her eyes, so I can tell you: She knows we are here, she knows we love her and she knows we are rooting for her throughout what will be a difficult journey," Obama told the cheering crowd.
House Minority Leader Nancy Pelosi, D-Calif., Sen. Kirsten Gillibrand, D-N.Y., and Rep. Debbie Wasserman Schultz, D-Fla., were in the room when Giffords opened her eyes, a congressional source told ABC News.
Giffords had her eyes open for about a minute total and was able to raise her whole arm, Gillibrand told ABC News, adding that everyone in the room was crying. Afterwards, Gillibrand said, the doctor declared it to be a major step forward for the patient.
"We had been telling her that she was inspiring the country with her courage and that we couldn't wait to take her out to pizza and a weekend away," Gillibrand said through a spokeswoman. "Then, after she heard our voices and the encouragement of Mark and her parents, she struggled briefly and opened her eyes for the very first time. It was a miracle to witness."
"My heart was overflowing with love for my friend Gabby today," Wasserman Schultz said in a prepared statement. "It was absolutely incredible to witness Gabby open her eyes. I am confident that the power of love, friendship and the prayers of a nation will help bring Gabby back to her family, her friends and her beloved constituents."
The president and first lady were greeted at the Tucson memorial by a standing ovation as they walked into the packed stadium.
"I have come here tonight as an American who, like all Americans, kneels to pray with you today, and will stand by you tomorrow," the president told the crowd.
You can read the president's full remarks HERE and click here for full ABC News coverage of the tragedy in Tucson.
As he listened to the ceremony before speaking, Obama was visibly emotional. Gifford's husband, space shuttle Capt. Mark Kelly, sat between the first lady and Secretary of Homeland Security Janet Napolitano.
Obama opened by quoting Psalm 46, saying, "There is a river whose streams make glad the city of God, the holy place where the Most High dwells. God is within her, she will not fall; God will help her at break of day."
The president focused on the victims and encouraged Americans to live up to the expectations of one of them, 9-year-old Christina Taylor Green.