(CNN) -- Arizona Rep. Gabrielle Giffords announced she will resign from Congress this week -- but not before finishing her "Congress On Your Corner" event that was interrupted by the shooting rampage that left six people dead and Giffords with a gunshot wound to her head.
At the private gathering Monday, Giffords will meet with some of the people who were at the event last year, including some who aided injured people and some who subdued the gunman, according to a statement from her office.
"A lot has happened over the past year. We cannot change that," Giffords, 41, says in a video on her website, speaking in a halting manner. She said she will resign to continue her recuperation from the brain injury she suffered when she was shot on January 8, 2011.
"I don't remember much from that horrible day, but I will never forget the trust you placed in me to be your voice," Giffords continues. "Thank you for your prayers and for giving me time to recover. I have more work to do on my recovery. So to do what is best for Arizona, I will step down this week."
Giffords, a Democrat, will submit a letter of resignation during the week to House Speaker John Boehner and Arizona Gov. Jan Brewer.
Brewer told reporters Sunday that within 72 hours of receiving that resignation, she expects to call a primary election sometime in April for political parties to pick their candidates for the state's 8th congressional district seat. That would be followed by a general election -- likely in June, according to the governor. The winner will head to Congress for the rest of Giffords' term, which ends in January 2013.
"Her recovery has been nothing less than a miracle," said Brewer, noting she spoke with Giffords' husband Mark Kelly earlier Sunday about the decision. "Who knows what's going to happen in the next two years. I don't believe we've seen the last of Gabby Giffords."
Before she steps down, Giffords will attend the State of the Union address Tuesday in Washington, her office said in a statement.
Rep. Debbie Wasserman Schultz of Florida, the Democratic National Committee chair, told CNN that Giffords -- a close friend -- came to the conclusion that she couldn't devote her full energies to both her job and her recovery.
The congressman's recent return to Tucson for the one-year anniversary of the shooting showed her "how challenging it would be. It came into focus then," her friend said.
"This decision is really quintessential Gabby Giffords," Wasserman Schultz added. "She needed to step aside for herself, so that her constituents could get full-time representation. She cares about them so much, that was her number one priority -- taking care of them."
President Barack Obama was effusive in his praise for the congresswoman, saying Giffords "embodies the very best of what public service should be." He added that her "cheerful presence will be missed in Washington (and) she will remain an inspiration to all whose lives she touched -- myself included."
"Over the last year, Gabby and her husband Mark have taught us the true meaning of hope in the face of despair, determination in the face of terrible odds, and now -- even after she's come so far -- Gabby shows us what it means to be selfless as well," Obama said in a statement.
Boehner, an Ohio Republican, said that Giffords "will be missed." And Brewer, the Arizona governor, lauded Giffords as a "noble public servant ... and a model of what can be accomplished with persistence and determination."
House Democratic leader Rep. Nancy Pelosi, D-California, called Giffords a "bright star" whose "message of bipartisanship and civility is one that all in Washington and the nation should honor and emulate."
"Her legacy in the Congress and her leadership for our nation will certainly continue," Pelosi said in a statement.
In her website video posted Sunday, Giffords says her public service career has not ended.
"I will return, and we will work together for Arizona and this great country," she says.
Earlier this month, Giffords joined thousands for a vigil in Tucson, one of several emotional events over the weekend to mark one year since the shootings. In addition to those killed, 13 people were injured in the shooting.
Prosecutors accuse Jared Lee Loughner, 23, of carrying out the attack, which purportedly targeted Giffords during the constituent meet-and-greet event outside a supermarket.
Giffords is still recovering from her injuries, and her right side remains weak. She has made few public appearances since the incident with some rare exceptions, such as casting a vote in Congress to raise the federal debt ceiling and conducting an interview with ABC's Diane Sawyer.
She has been undergoing intensive rehabilitation in Houston, Texas, but returned to Tucson several times, according to her office.
Pia Carusone, the congresswoman's chief of staff, said recently that Giffords had steadily increased her workload as her condition improved.
"As the year wore on, we were able to plug the congresswoman in more," Carusone said. "Now we talk regularly over video chats and telephone. She's gotten more and more involved the better she gets."
Still, Wasserman Schultz said Sunday night that Giffords now realizes that "her recovery now is more likely to stretch into years, rather than months."
"I know she's coming back; she wants to come back to public service," the Florida congresswoman said, adding that Giffords is stepping down thinking "it's better to focus on coming 100% back."
Loughner, the man accused of targeting her last year outside a Tucson supermarket, potentially faces the death penalty if convicted on charges of murdering six people -- including the chief federal judge of Arizona, John Roll. Loughner has been diagnosed as schizophrenic and has spent time on suicide watch while in custody and is undergoing treatment in Springfield, Missouri.
A federal appeals court in May cleared the way for him to be forcibly medicated over the objections of Loughner and his attorney.
Giffords herself worked at PricewaterhouseCoopers and as CEO of El Campo Tire, her family's business, before being elected to the Arizona House of Representatives in 2000. Two years later, she became the youngest woman elected to the Arizona state senate.
She won a November 2006 election to earn her spot in the U.S. Congress, then captured two other terms. Kelly, her husband, is a retired Navy captain and astronaut.
A flood of people posted comments on Giffords' Facebook page Sunday under her video -- praising the congresswoman for her courage, voicing their continued support and expressing hope that she'll one day return to public office.
One person wrote, "I am so thankful you are taking care of you. We can wait."
Another commenter called Giffords an "inspiration" and a "great example."
"It's so sad to see you leave but I know we'll see you back soon. Be well. You are loved," he wrote.
CNN's Tom Cohen and Dana Bash contributed to this report.