With the flood of news events streaming across our screens these days, little seems truly shocking anymore. We careen from one cataclysm, conflict or scandal to the next, never lingering long on any of them.

But sometimes an event is so terrible that it causes all of us to drop whatever we're doing and reflect. The assassination of John F. Kennedy in a 1963 Dallas motorcade -- the unforgettable sight of the president being whiplashed by a sniper's bullet -- had that kind of power. So did the video of the two jets slamming into the World Trade Center towers -- the explosion of flames, the choking waves of smoke, the desperate people trying to escape, the towers collapsing -- on Sept. 11, 2001.

And then there was the shooting of Gabrielle Giffords in Tucson, Ariz., in 2011.

What makes the massacre in that Safeway parking lot so haunting and distressing? Certainly, the story has all of the elements that make for memorable drama: A young, genuinely nice congresswoman is shot in the head by a mentally disturbed, glassy-eyed young man; six bystanders, including a child, die, but somehow, with the support of skilled doctors, her astronaut husband and well-wishers nationwide, she survives to deliver a message of tolerance.

"Another random act of violence": That's what many call such incidents, as if they remain inexplicable. Yet, as journalist and author Tom Zoellner illuminates in our cover story, the Safeway shooting, like other historic events, gains true meaning and power from its context. To understand it, Zoellner argues, you must first understand Arizona, a state shaped by sprawling growth, anti-federal and anti-immigrant anger, and a love of guns. Zoellner, who has known Giffords for years, grew up in the dysfunctional suburbs of Tucson -- as did killer Jared Lee Loughner, who bounced from one low-paying service job to the next before falling through the cracks, where no one could help him.

Of course, Arizona also nurtured Gabby Giffords, and Zoellner finds hope for both Arizona and the nation in her remarkable fortitude and upbeat attitude, as well as in the friends, colleagues and strangers who assisted her and the other victims on that fateful day. As Zoellner writes: "In that bloody moment, with no time to think, some of them stepped in front of bullets to save loved ones, suffering serious and even fatal wounds. Amid all the chaos and horror, people took the crucial steps that saved Gabby's life despite the bullet that tore through her brain. They formed a community on the spot, one stitched together by bullets."

As we plunge into another rhetorically charged election season, dominated by the specters of fear and anger, we need to ask: Have we learned anything at all from the blood on the pavement at the Tucson Safeway?