Early on Wednesday afternoon, Marjory Stoneman Douglas High School, in Parkland, Florida, had a fire drill, an eleventh-grader named Gabriella Figueroa told MSNBC’s Brian Williams. “Then we heard gunshots,” Figueroa said. “Then it went to code red. And then it was crazy.”

An individual with deadly intent was in the school building, holding an assault weapon that was designed for fighting wars. As Figueroa’s use of the term “code red” indicated, such an event is no longer considered an aberration. All across the country, school boards drill their teachers and students in how to respond to such an emergency. Code yellow: turn cell phones to silent, return to the classroom, and follow the teacher’s instructions. Code red: find a secure area immediately, lock the door, close the blinds, turn off the lights, do not move.

This lockdown wasn’t a drill, of course. By the time it was over, seventeen people had been shot dead, and more than a dozen had been wounded. “Bodies were lying in the hallway,” another eyewitness told Fox News. “People were killed in the hallway.” Police later identified the suspected killer as Nikolas Cruz, a nineteen-year-old former student who had been expelled for discipline problems.

After Cruz fled the scene—he was arrested shortly after the shooting, in neighboring Coral Springs—news helicopters captured footage of students walking and running from the school, some of them carrying flowers and cards. It was Valentine’s Day, after all. By that point, the authorities had secured the area around the school. There were heavily armed cops, police cars, bomb-squad trucks, and F.B.I. vehicles. The mayor of Parkland, a former teacher named Beam Furr, told CNN, “It’s all being fairly well coördinated, and everyone is doing everything they can.”

But were they? On Twitter, President Donald Trump offered his “prayers and condolences to the families of the victims,” adding that “no child, teacher, or anyone else should ever feel unsafe in an American school.” Fox News interviewed Marco Rubio, Florida’s junior senator, who has an A-plus rating from the National Rifle Association. “I hope people reserve judgment.... The facts of this are important,” Rubio said. As soon as the facts are clear, Rubio went on, “we can have a deeper conversation about why these things happen.” The forty-six-year-old Republican added, “It’s a terrible situation. It’s amazing the amount of carnage that one individual can carry out in such a short period of time.”

Yet some pertinent facts are already known. According to local police, Cruz was armed with an AR-15 assault-style rifle—the same type of gun that Adam Lanza used to kill twenty-six pupils and staff at Sandy Hook Elementary School, in December, 2012. Evidently, Rubio still isn’t aware of the power of such weapons, which fire bullets that can penetrate a steel helmet from a distance of five hundred yards. When fired from close range at civilians who aren’t wearing body armor, the bullets from an AR-15 don’t merely penetrate the human body—they tear it apart. It “looks like a grenade went off in there,” Peter Rhee, a trauma surgeon at the University of Arizona, told Wired.

To spare the families of the victims—and the public at large—additional anguish, these sorts of details are often glossed over in the aftermath of mass shootings. But it’s surely long past time that we acknowledged these facts, and that we begin to more fully discuss the complicity of N.R.A.-backed politicians like Rubio, and Florida’s governor, Rick Scott, in maintaining the environment that allows these tragedies to happen again and again and again.

One of the first duties of any government is to protect its citizens, through collective action, from violent threats they’d otherwise have to fend off themselves. Even most libertarians accept this principle. But when it comes to mass shootings, the Republican Party falls back on constitutional arguments that have no proper basis in history, and it refuses to budge from this stance. Nothing can shift it—not Sandy Hook, not the Orlando night-club shooting, not the Las Vegas massacre, not weekly shootings in schools. (According to the Guardian, Wednesday’s attack in Parkland was the eighth school shooting this year that has resulted in death or injury.) Nothing.

Further Reading New Yorker writers respond to the Parkland school shooting.

The Democrats aren’t entirely blameless, either. In 2009 and 2010, when they controlled the White House and both houses of Congress, they failed to take some steps that were obviously necessary, such as closing the gun-show loophole for background checks and reinstating the Clinton Administration’s ban on assault weapons, which the Bush Administration allowed to expire.

The Republicans bear the primary responsibility, though. Ever since Sandy Hook, it is their craven subservience to the gun lobby that has prevented meaningful action, even as the carnage that Rubio referred to has continued. “Turn on your televisions right now and you are going to see scenes of children running for their lives,” Chris Murphy, the junior Democratic senator for Connecticut, said on the Senate floor on Wednesday afternoon. “Let me just note once again for my colleagues: this happens nowhere else other than the United States of America. This epidemic of mass slaughter, this scourge of school shooting after school shooting, it only happens here. Not because of coincidence, not because of bad luck, but as a consequence of our inaction. We are responsible for a level of mass atrocity that happens in this country with zero parallel anywhere else.”

The key concept in that excellent peroration was responsibility. Even with the blood of defenseless children flowing along the corridors of schoolhouses, the U.S. government has abdicated its duty to protect. And that, it bears repeating ad nauseum, is a national disgrace.