The former student charged with stalking and killing 17 people at Marjory Stoneman Douglas High School in Parkland, Fla., wasn’t a terrorist. At least, not by the usual definition. From what we know now, he wasn’t out to terrorize the population as a way of advancing a cause. He evidently was a disturbed misfit who had been expelled from the school, who legally bought a semi-automatic AR-15 rifle, who set off the fire alarm so students would come out of classrooms.

We don’t know his motive, but we raise the issue of terrorism here because these horrific mass shootings now happen so frequently that they demand a response on the same scale as the nation mustered after the Sept. 11 attacks.

When the World Trade Center towers fell, when airplanes crashed into a Pennsylvania field and the Pentagon, Americans mourned their dead and then. confronted the threat.

Americans acted. To fortify national security at airports, federal buildings, public venues. To revamp the nation’s intelligence services and surveillance laws. To attack terrorist leaders and networks overseas.

This nation faces a comparable challenge to its resolve now.

Ryan Kadel, a 17-year-old Douglas High School senior who survived the Florida attack, spoke for millions of us: “I’m kind of surprised it happened here, but I’m not really shocked. School shootings happen all the time, and then the news just forgets about them.” Another 17 victims, another 17 families.

We don’t believe that these shootings are impossible to stop — or that the carnage at schools, workplaces, churches and beyond is a status quo that Americans should accept.

Things change when enough Americans determine that they must. When people get outraged by these massacres and stay outraged.

After shootings in a South Texas church in November, we outlined several ways for Congress to stop the armed and deranged from targeting innocents. Those include: requiring background checks for every gun purchase, including those at gun shows and transactions between private parties; limiting the capacity of magazine clips, forcing assailants to frequently reload; and banning “bump stock” devices that convert semi-automatic rifles into machine gun-like weapons.

We’ll keep urging sensible steps to end the carnage until politicians are jolted to action.

The inertia, however, is powerful. After a gunman killed 58 people at an outdoor country music festival in Las Vegas last fall, members of Congress vowed to outlaw bump stocks. Even the National Rifle Association agreed that bump stocks “should be subject to additional regulations.” But those efforts quickly bogged down in political disputes. Result: Nothing happened.

Will the Florida attack soon slip off the nation’s radar the same way that the 1999 killing of 12 students and a teacher at Columbine High School in Colorado did? The same way as the 2012 massacre of 20 students and six adults at Sandy Hook Elementary in Newtown, Conn.?

We hope not.