Tucson, Arizona (CNN) -- In between consoling those touched by Saturday's Arizona shooting and warning the nation against politicizing the tragedy, President Barack Obama delivered some good news in his address at a Tucson memorial event on Wednesday.
Rep. Gabrielle Giffords of Arizona has opened her eyes for the first time since being shot four days ago.
"There is nothing I can say that will fill the sudden hole torn in your hearts," Obama said. "But know this: The hopes of a nation are here tonight."
The attack killed six and left Giffords fighting for her life.
Obama told a crowd of thousands that he visited Giffords earlier on Wednesday and that her husband told him that shortly after the president left her room, "Gabby opened her eyes for the first time."
"Gabby opened her eyes so I can tell you know she knows we are here, she knows that we love her and she knows that we are rooting for her through what will undoubtedly be a difficult journey," Obama said.
Obama and his wife, Michelle, sat next to Giffords' husband, astronaut Mark Kelly, throughout the ceremony, and next to Daniel Hernandez, an intern in Giffords' office who tended to the congresswoman's wounds after she was shot.
Obama called Hernandez a hero in his speech Wednesday, though Hernandez rejected that description in an earlier speech at the memorial event.
The president spoke at the University of Arizona's McKale Memorial Center, which the school said held just under 14,000 people on Wednesday night, with an overflow crowd of 13,000 outside.
Obama spoke about Giffords and briefly eulogized each of those killed in the attack before moving on to warn Americans against assigning blame for the attacks to those other than the gunman.
"At a time when our discourse has become so sharply polarized -- 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," Obama said.
"Scripture tells us that there is evil in the world, and that terrible things happen for reasons that defy human understanding," he said. " ... Bad things happen, and we must guard against simple explanations in the aftermath."
"What we can't do is use this tragedy as one more occasion to turn on one another," he said later.
Obama's speech was frequently punctuated by applause and cheers from the crowd, at times seeming to belie the somber reason for the memorial.
But Obama sounded an uplifting tone, saying of the victims: "Our hearts are broken by their sudden passing. Our hearts are broken -- and yet, our hearts also have reason for fullness."
Beyond Hernandez, the president praised those who tackled the gunman as he stopped to reload and the medical staff who treated the wounded.
"These men and women remind us that heroism is found not only on the fields of battle," Obama said. "They remind us that heroism does not require special training or physical strength. Heroism is here, all around us, in the hearts of so many of our fellow citizens, just waiting to be summoned -- as it was on Saturday morning."
"It was pretty much what the nation needed to hear at this time," said Lorenzo Cotton, a retired architect who attended the speech.
"Tucson is a great place with a lot of great people," Cotton said, adding that Obama's speech "put Tucson back in a positive light. It is a community and it is a place where we all get along and, together, care for each other."
Other public officials took the stage before Obama, with many invoking scripture.
"We will remember how to smile again," Arizona Gov. Jan Brewer said. "We will go forward together."
Secretary of Homeland Security and former Arizona Gov. Janet Napolitano, Brewer's predecessor as governor, read from the book of Isaiah, while Attorney General Eric Holder reads from the Second Letter of Paul to the Corinthians.
The crowd was dotted with other prominent Arizonans, including Sen. John McCain and retired Supreme Court Justice Sandra Day O'Connor.
Earlier Wednesday afternoon, the Obamas visited with Giffords and with other survivors of the shooting and the medical staff that treated them at Tucson's University Medical Center.
Rep. Debbie Wasserman Schultz, D-Florida, and Sen. Kirsten Gillibrand, D-New York, said they were with the congresswoman when she opened her eyes for the first time since the shooting.
"You could see she was focusing and Mark said, 'Gabby if you can see me, give me the thumbs up' and not only did she give the thumbs up she raised her entire hand," Gillibrand said, referring to Giffords' husband.
"The doctors couldn't believe it," Gillibrand said. "She went from opening her eyes really just in slits to opening them nearly fully."
Obama visited about 100 people at the hospital, a White House aide said.
Napolitano and House Minority Leader Nancy Pelosi traveled with the Obamas.
Giffords' recovery is "going as anticipated," and doctors are seeing what they want to see so far, the hospital treating her said earlier in the day.
Peter Rhee, chief of emergency medicine at University Medical Center in Tucson, said "none of the downward events have occurred at this time" in her recovery.
Doctors have decreased the amount of sedation they are giving her, and she is "becoming more and more spontaneous all the time," Rhee added.
Also Wednesday, Giffords' congressional office released a statement thanking Americans for their support since the shooting.
"The outpouring of support from the people of Arizona and Americans across the country has been truly moving," the statement said. "We appreciate everyone's thoughts and prayers during this difficult time."
Giffords' office acknowledged the bipartisan response in the Congress to the tragedy. " ... Starting with Speaker Boehner and Leader Pelosi, staff and Members from both sides of the aisle have reached out in words and deeds to help our office in our time of need," the statement said.
Of the six patients the hospital is still treating from Saturday's shooting, Giffords is the only one in critical condition. Two others are in serious condition, the other three are in fair condition, Rhee said.
A 9-year-old girl and Arizona's chief federal judge, John Roll, were among those killed at a constituent meeting Giffords was holding at a Tucson supermarket.
Authorities say Giffords was the target of Saturday's shooting. Thirteen people suffered gunshot wounds, the Pima County Sheriff said in a statement Tuesday night. Some other people were injured trying to flee the scene, the sheriff said.
Tucson resident Jared Loughner, 22, has been charged in the attack.
Giffords' Chief of Staff Pia Carusone, meanwhile, said the Giffords family is "very strong, very supportive. You know, she's a young, healthy person who is not only physically strong, but mentally resilient and, you know, they're rising to the occasion."
Carusone added, "They've got a long road ahead of them, not just the physical recovery, but the tragedy that this community is having to absorb is -- it's monumental and it's going to be ... a difficult thing to get through."
Meanwhile, Arizona state lawmakers passed legislation Tuesday barring protesters at funerals from getting within 300 feet of services. Brewer, who visited the injured Tuesday, later signed the bill.
The action, according to Arizona House Republican spokesman Daniel Scarpinato, was in direct response to the controversial Westboro Baptist Church's announcement that it would picket the funeral of 9-year-old victim Christina Green on Thursday.
Shirley Phelps-Roper, a spokeswoman for Westboro, told CNN that the church has decided not to protest at the girl's funeral. She said her group made a deal with a radio host not to protest there in exchange for airtime. However, she said church members would protest at the funeral of U.S. District Judge John Roll and other victims on Friday.
The Steve Sanchez Radio Show on KXXT AM in Phoenix offered the group 30 minutes on his show on Saturday in exchange for not protesting at Green's funeral. The deal was established through an e-mail exchange, which was forwarded to CNN.
In one e-mail, a representative of the show informs Phelps-Roper that the group will have to avoid profanity and that the platform will "allow you to express your views and allow you as guest and Steve Sanchez as host to have a civil dialogue and discord." Phelps-Roper responded that the group had no problem with the rules.
CNN's John Sutter contributed to this report.