IT TOOK A MATTER of seconds during a gathering with constituents at a Tucson shopping center for Rep. Gabrielle Giffords’s (D-Ariz.) life to be profoundly transformed. Ms. Giffords was one of 19 people wounded or killed there last year, allegedly by a deranged young man who inflicted unspeakable damage with the help of a semi-automatic weapon and an extended magazine clip. The bullet that pierced Ms. Giffords’s head left her clinging to life; hers has been a remarkable rehabilitation over the past 12 months, during which she has learned to walk and speak again.

But Ms. Giffords has made clear that this journey is far from over. “I have more work to do on my recovery,” she said during a two-minute video released Sunday. She announced that she would not seek reelectionfrom Arizona’s 8th Congressional District and would step down from her post this week after attending President Obama’s State of the Union address on Tuesday evening. A special election will be held in the next few months to temporarily fill the seat before voters return to the polls in the fall to select a permanent replacement.

In announcing her decision to resign, Ms. Giffords displayed the grace and buoyancy of spirit that have come to be hallmarks of her tenure. She could have exploited voters’ sympathy to retain the seat; instead, she placed the needs of her constituents first. Implicit in the decision to step down — or as she put it, “to do what’s best for Arizona” — was an understanding that she probably could not carry out the demands of public life before recuperating further.

Ms. Giffords did not refer directly to the events of Jan. 8, 2011, other than to say that she remembered little about that horrific day. But it would be a disservice to her life and that of the others directly affected by this, and tragedies like it, to ignore the factors that precipitated the violence: the easy access to guns; the availability of accessories such as extended clips that make deadly weapons all the more lethal; and a porous and shoddy regulatory system that too often fails to keep these weapons out of the hands of dangerous or dangerously unstable individuals.

Mr. Obama last year delivered his State of the Union just weeks after the Tucson massacre and in the presence of victims’ family members. Yet he, like so many politicians intimidated by the gun lobby’s muscle, could not muster a single word about the need for reasonable gun control measures to ward off such violence in the future. Perhaps he will find the courage to speak up this year, as Ms. Giffords looks on during her last State of the Union as a member of Congress.