Correction: An earlier version of this essay incorrectly reported that 13 people were killed in the Jan. 8, 2011, attack at a supermarket in Tucson, Ariz., that seriously wounded then-U.S. Rep. Gabrielle Giffords. Six people died in the attack. This version has been corrected.

We’ve moved on, apparently. Barely 48 hours after a gunman murdered 12 people and injured others in another U.S. bloodbath, the national news media had other things on their minds.

On Fox News, the midday panel discussed something called “the Hiccup Girl trial.”’s lead story was about the early retirement of an NFL player (also big on Yahoo: “Forget Pumpkin Pie! Say Hello to Your New Favorite Pumpkin Dessert”). MSNBC had the jump on a “brain-eating amoeba” affecting someone, somewhere in Louisiana. CNN, struggling for decency and dignity, coupled coverage of the shooting’s aftermath with live updates about the safe return of an abducted 14-year-old girl in Georgia.

This was a day after Britney Spears appeared on “Good Morning America” to announce her new Las Vegas show. “Only on GMA!,” the promo bragged.

No one announced a telethon for the victims of the Washington shootings or broke out ribbons of any color. Major League Baseball briefly considered playing a game a few blocks from where the bodies lay. No problem: The Nationals played a doubleheader Tuesday, instead.

The desire to get back to something else, to distract, is surely understandable; the news from the Navy Yard was grim. But the national news media’s quickly fading interest suggests there was something ordinary and familiar, almost banal, about Monday’s body count.

It’s not just that we’ve seen this before, even though we have: There were 78 mass public shootings in the United States between 1983 and 2012, according to a Congressional Research Service study, which toted up 547 dead and 476 injured people from this mayhem.

But not all senseless, horrendous crimes are equal in the national consciousness. It’s as though the events of Monday morning, after the first breathless reports, failed to jog the media’s central nervous system and, by extension, the public’s, into a sustained response.

The relative non-reaction might be explained by what Monday’s tragedy was not. It wasn’t Tucson, with its six dead and its now-famous survivor, former congresswoman Gabby Giffords. It wasn’t Aurora, Colo., with its ordinary, anyone-could-have-been-there locale, a movie theater. It wasn’t Nickel Mines, Pa., with the horror of dead Amish schoolchildren. Nor was it Columbine, Colo., or Virginia Tech, with so many promising young lives cut short, nor Fort Hood nor Boston, with the specter of terrorism.

And it wasn’t Newtown, Conn., with its monstrous slaughter of small children and the adults who had taught and protected them.

The cynical truth is that the Navy Yard murders — we’ve yet to agree on the shorthand name for this event — had neither the kinds of victims nor the story that sustains media interest and public revulsion.

Those who study crime can tell you what excites and interests the public, which is not just about titillation. Outrage is important. Sustained public interest stirs the outcry for change. The Navy Yard murders had only one of these dimensions: They occurred in the District, in the midst of the national media, making them instantly visible.

Beyond that, ennui.

The event took place in a seemingly secure but otherwise obscure government building, blandly known as Building 197, in a city filled with better-known locales. The victims were mostly government employees, not the soldiers or sailors or law enforcement officers we reflexively memorialize as heroes. And they were mostly middle-aged people, not the children, teenagers or young adults whose deaths create greater spasm of shock.

Some of the mystery of the crime — if there’s any “mystery” in the shattered logic of a deranged mind — died with the alleged shooter, Aaron Alexis. He will have no perp walk, no long and agonizing court trial. He appears not to have been an ideologue or a terrorist. He was a young man with demons and guns; we have seen his kind before, in Jared Loughner, James Holmes, John Hinckley and other infamous shooters.

He was also African American, and this apparently matters, says eminent criminologist James Alan Fox. “It’s not nice to say it, but white America tends to be more intrigued about the minds and motives of white murderers,” said Fox, who is a professor at Northeastern University. “There have been black [mass shooters], but it’s hard to remember who they are. The D.C. sniper is an exception.”

Fox, who has been studying mass murder since the early 1980s, sees a dismaying jadedness in our national response to such spectacular acts of inhumanity. Even as overall gun violence has fallen precipitously, what shakes the national scales has graduated, higher and higher, he says. “When four people were killed [in a shooting], it was always covered” nationally, he said. “Of course now, four people doesn’t get covered. It doesn’t rate.”

So, even the news of 12 dead people fights for airtime with Britney Spears and the Hiccup Girl.

Move along. Not much to see here. Except your country, circa 2013.