Then that moment when the local law enforcement official, face blanched by the sorrow of what must be imparted, appears before cameras. On Wednesday, it was Scott Israel, the sheriff of Florida’s Broward County, who stepped forward to announce the toll of a massacre inside Marjory Stoneman Douglas High School: 17 children and adults dead, another 16 wounded.

The suspect in custody: Nikolas Cruz, 19, a former student who was expelled from the school and who unnerved acquaintances with his obsession with violence and guns. After the slaughter, the police said, he dropped his legally purchased rifle — an AR-15 — ran out of the school, and bought a drink at a Subway.

“There are no words,” Sheriff Israel said.

Other than offers of thoughts and prayers. Or “prayers and condolences,” as President Trump wrote on Twitter Wednesday afternoon.

Deadly shootings in schools — that is, the killing of children in sanctuaries of learning — have become a distinctly American ritual, the rote responses as familiar as a kindergarten recitation of the Pledge of Allegiance.

Part of the accepted script is the repeated invocation of the place names of Columbine and Sandy Hook. But these massacres deserve to be more than mere reference points, if only to underscore the protracted inaction of Congress to respond — an inaction that, judging by the Capitol Hill partisanship on display Thursday, seems concretized.

For the record: In 1999, two seniors at Columbine High School in Colorado killed 12 students and one teacher in a carefully orchestrated attack. And in 2012, a gunman walked into the Sandy Hook Elementary School in Newtown, Conn., and killed 20 children, none older than 7, and six adults.

The nation was shocked, then doubly shocked. But the emerging American tradition of school shootings has continued.

Even the dark humor in the headline of a satirical story in The Onion, first published in 2014, has since been stripped of any mirth, leaving only a dark, accepted truth: “‘No Way to Prevent This,’ Says Only Nation Where This Regularly Happens.”

Jason Roeder, the author of that often-recycled headline, underscored the national sameness of these school shootings on Twitter on Wednesday, saying: “When I wrote this headline, I had no idea it would be applied to the high school a mile from my house.”

Last month, in the wake of another school shooting that you may have already forgotten — a 15-year-old boy killing two classmates and wounding 18 other people in Kentucky — a former F.B.I. agent reflected on the lack of shock that she and her colleagues felt over the repetition of these incidents.