WATCHING RELIEVED parents reunite with their children in the immediate aftermath of Wednesday’s mass shooting at a South Florida high school, it was impossible not to think about the others — the less fortunate ones. The parents frantically calling their children’s cellphones, hearing their panicked calls go straight to voice mail, slowly coming to understand that they would never hug their child again.

In the latest school shooting — a phrase so grotesquely, uniquely common to the United States — 17 people were killed and 15 injured. Among the dead: a 17-year-old senior excited about his upcoming college swimming scholarship; a football coach who jumped in front of the gunman to shield students from the bullets; a 15-year-old girl remembered for her love of soccer and writing.

The rampage just before the close of classes at Marjory Stoneman Douglas High School was at least the eighth shooting this year at a U.S. school or college resulting in injury or death. It was the worst school shooting since 26 children and adults were slaughtered at Sandy Hook Elementary School in Connecticut in 2012. And we can say with tragic certitude it won’t be the last needless loss of life resulting from the wash of guns in this country and the refusal of national lawmakers to tighten controls over who can buy a gun and what kinds of weapons may be owned.

That the suspected 19-year-old gunman in the Florida shooting was able to legally purchase an AR-15 rifle despite concerns about his mental health, a social media fixation with guns, alleged involvement with a white-nationalist group and boasts about killing animals underscores the complete failure of America’s political class to come to grips — or even to try to come to grips — with gun violence. Said teacher Melissa Falkowski, who sheltered 19 students in a classroom closet during the shooting, “The frustration is that we did everything that we were supposed to do . . . and still to have so many casualties. . . . I feel today like our government, our country has failed us and failed our kids and didn’t keep us safe.”

No question there were several factors contributing to Wednesday’s shooting. The accused shooter is a troubled young man with a history of discipline problems. Those who knew him, as well as people in law enforcement, appear to have responded inadequately to signs of danger.

But here is the key fact: This country has no monopoly on troubled young men. We have no monopoly on hate groups. We aren’t the only place where people miss signs of danger in troubled young men. What distinguishes the United States from the developed world is our open market in the weaponry of war — in weapons whose chief purpose and selling point is their obscene ability to kill as many people as possible in the shortest burst of time.

Is it any surprise that the weapon used in this week’s carnage was the same style of semiautomatic assault rifle that was used with deadly efficiency at a concert in Las Vegas, a Texas church, an Orlando nightclub, a Connecticut elementary school? These weapons designed for combat, accompanied by multiple ammunition magazines, have become the weapons of choice for mass shooters. It is time for a national ban on their sale and possession. Now, before the next set of parents face the unimaginable agony of the phone call that never gets answered.