Updated at 10:49 p.m. ET
TUCSON, Ariz. - During his speech at the "Together We Thrive: Tucson and America" Wednesday night, Mr. Obama told the crowd, referring to U.S. Rep. Gabrielle Giffords, who was injured in the shooting tragedy Saturday, "Gabby opened her eyes for the first time."
Mr. Obama delivered the news to cheers from the crowd. The direct reference to Giffords was a deviation from the prepared remarks in his speech.
Scroll down to see video clips from Mr. Obama's speech.
Mr. Obama and first lady Michelle Obama arrived at the memorial to cheers from the crowd Wednesday night in Tucson. In his remarks, Mr. Obama said in a reference to the six people killed Saturday, "Our hearts are broken - and yet, our hearts also have reason for fullness."
That's when Mr. Obama followed with, "Gabby opened her eyes for the first time. I can tell you, she knows we are here, she knows we love her, and she knows that we are rooting for her through what is undoubtedly going to be a difficult journey We are there for her."
Later in the speech, making reference to Christina Taylor Green, the 9-year-old girl who wanted to be a politician who was shot and killed Saturday, Mr. Obama said, "I want us to live up to her expectations. I want our democracy to be as good as she imagined it. All of us - we should do everything we can to make sure this country lives up to our children's expectations."
He closed with, "May God bless and keep those we've lost in restful and eternal peace. May He love and watch over the survivors. And may He bless the United States of America."
Other speakers at the "Together We Thrive: Tucson and America" included University of Arizona president Robert N. Shelton, student body president Emily Fritze, Daniel Hernandez Jr., the intern credited with saving Giffords' life by applying pressure to her wound, Arizona governor Jan Brewer, Secretary of Homeland Security Janet Napolitano, Attorney General Eric Holder and Mr. Obama.
Beforehand, Mr. Obama visited with families of the deceased in Saturday's shooting in Tucson.
Also present are attorney general Eric Holder, Senators John McCain (R) and Jon Kyl (R) from Arizona, and Sen. John Barrasso (R-Wyo.)
Mr. Obama visited Congresswoman Gabrielle Giffords and her husband in the ICU on the second floor of University Medical Center in Tucson. He stayed for with Giffords and her husband for a nine-minute visit, said press secretary Robert Gibbs in a statement. The doctor who led Mr. Obama through the hospital was Dr. Peter Rhee.
Mr. Obama flew to Arizona Wednesday and headed straight to Rep. Gabrielle Giffords' bedside to pay his respects to the wounded lawmaker as he sought to unify a mourning nation.
Mr. Obama and first lady Michelle were visiting privately at University Medical Center with Giffords and other victims of the weekend shootings that killed six people and wounded 13. He was then meeting with family members of those killed before speaking at a nighttime memorial service in Tucson.
"The president wanted to begin this solemn trip by stopping first at the hospital where Congresswoman Giffords and others continue to recuperate," White House spokesman Robert Gibbs told reporters traveling with the president. Giffords was the target of the first assassination attempt on a member of Congress in decades.
Inside the Intensive Care Unit at the hospital, the president spent about 10 minutes with Giffords and her husband, Mark Kelly. He also met with four other victims from the shooting, including two of Giffords' staff members who were wounded in the rampage. The president and the first lady also met with members of the trauma resuscitation team who were the first people to treat the victims.
Back on Capitol Hill, Giffords' House colleagues praised her and the other shooting victims and insisted that violence would not silence democracy.
"We will have the last word," declared new House Speaker John Boehner. He fought back tears as he described Giffords' battle to recover from Saturday's gunshot wound to her head.
The shootings, apparently a brazen attempt to kill a member of Congress, shattered a Saturday event Giffords had organized outside a grocery as a way for her constituents to chat with her.
Threats against lawmakers are not uncommon, but violence is rare. The last killing of a serving member of Congress was in November 1978, when Rep. Leo Ryan, a California Democrat, was murdered in the South American jungle of Guyana while investigating the Jonestown cult.
Police say the man accused of the shootings, 22-year-old Jared Lee Loughner, shot Giffords as well as many in the line of people waiting to talk with her. The attack ended when bystanders tackled the man. He is in jail on federal charges as police continue to investigate.
Four days after the shootings, Giffords was making small movements on her own. The three-term Democrat was expected to live. Mr. Obama was joined on Air Force One by Republican members of Arizona's congressional delegation, House Democratic leader Nancy Pelosi, Supreme Court Justice Anthony Kennedy, Attorney General Eric Holder and Homeland Security Secretary Janet Napolitano.
By midafternoon, the university said 17,000 people were in line for the event, exceeding the arena's intended capacity. Overflow seating was set up at the school's football stadium, with a video of the proceedings to be played on the scoreboard screen.
The memorial service was an important part of the mourning process for some of those who had lined up hours in advance to gain a seat.
"If we don't say goodbye and have a chance to say goodbye in an appropriate way, it will linger," said Patty Sirls, 62. "So, for me, it's a closure."