The Colorado shooting rampage brought the nation to a virtual standstill as we tried to absorb the horror.

Once again—after Columbine, after Virginia Tech, after the attack on U.S. Rep. Gabrielle Giffords—we watched the chillingly familiar story unfold. This one happened in the Denver suburb of Aurora, where a crazed young man, in a gas mask and bulletproof vest and armed to the teeth, opened fire in a theater full of movie fans at the midnight screening of “The Dark Knight Rises.” Had one of his weapons not jammed, the grim toll of 12 dead and 58 wounded would surely have been higher.

Police said that James Holmes, the 24-year-old suspect, had planned his deadly attack for months, stockpiling weapons and combat gear and ordering a mind-boggling 6,000 rounds of ammunition on the Internet. Before leaving home to commit his evil deed, he booby-trapped his apartment.

We reacted, as we do in times of tragedy, by coming together in solidarity with the survivors of the attack and the families of victims; we prayed for the dead.

Barack Obama and Mitt Romney suspended their presidential campaigns and offered condolences and prayers. Pope Benedict XVI expressed sadness, saying he was “deeply shocked by the senseless violence.”

A joint statement by newly installed Archbishop Samuel J. Aquila of Denver and his auxiliary, Bishop James D. Conley, said that for those who were killed, “our hope is the tender mercy of God,” and for those who were wounded—physically, emotionally and spiritually—“our hope is in their recovery and renewal.”

Yet even in the midst of such indescribable heartbreak, there were many scenes of extraordinary heroism and self-sacrifice by “ordinary” Americans. Three young men—Jon Blunk, Alex Teves and Matt McQuinn—used their bodies to shield their girlfriends from the gunshots and lost their own lives instead. Allie Young, 19, survived a shot in the neck because her friend Stephanie, 21, lay next to her to stanch the flow of blood, refusing to run even while bullets were still flying.

There were incidents that could truly be called miraculous, as well. Gifted young musician Petra Anderson, 22, survived a shotgun blast that sent a pellet through her skull only because a rare and previously unknown birth defect in her brain structure caused it to miss vital spots. In another story, with a “miraculous” and sad side, pregnant Ashley Moser and her unborn baby both survived three shots from a semiautomatic rifle, one of which punctured Ms. Moser’s abdomen. But the woman’s 6-year-old daughter Veronica, the youngest of the victims, was killed.

As often happens in the aftermath of such a horrific event, there were calls for tighter gun control laws and more restrictions on the purchase of ammunition. We have supported stricter controls on guns in the past and we recommit to that today. We now see that how and who acquires the implements is important too. Who, besides a madman or a member of a self-styled militia, would believe they need 6,000 rounds of ammunition? And should it be easily available to anyone with a computer and a mailing address? These are questions our leaders need the courage to address.

As we pray for those killed and injured in the attack, we also would do well to heed the words of Archbishop Aquila and Bishop Conley in their prayer for the conversion of the shooter. “Evil ruled his heart last night,” they said the next day, and “only Jesus Christ can overcome the darkness of such evil.”