Less than 24 hours after yet another mass shooting in America, the youngest fatalities a 6-year-old boy and a 13-year-old girl, authorities said they were still seeking a motive.

It seems the 19-year-old shooter gave us one.

“Why are you doing this?” a witness heard someone shout.

The response:

“Because I’m really angry.”

From those mass shooters who have attacked the innocent before, we know it’s a specific strain of anger — deep, repressed, biblically vengeful — felt most commonly by young men, almost always white, who report feeling alienated, dispossessed, misunderstood, victimized and all too often rejected by women.

Their chosen outlet is the mass slaughter of innocents, carnage at places the rest of us once deemed safe — schools, hospitals, places of work and worship, concerts, carnivals — all meant to hold us hostage, in fear of the next reprisal we’re not responsible for and won’t see coming.

Little is known yet about this shooter’s history — and I refrain from using his name, since infamy is part of what these shooters seek — but so far, he fits the profile of those who’ve come before, the rage-induced young men we first encountered through Columbine and later Sandy Hook, Aurora, Charleston, Virginia Beach, the STEM school shooting in Colorado, Charlotte, the Poway synagogue shooting in California, the Louisiana shootings in two parishes, the Sebring shootings in Florida (those last six this year alone), the Mercy Hospital shooting, the Thousand Oaks shooting, the Tallahassee yoga studio shooting, the Jacksonville Landing shooting, the Art All Night shooting in New Jersey, the Santa Fe HS (Texas) shooting, the Nashville Waffle House shooting, the Marjory Stoneman Douglas HS shooting — and far too many more to mention, but all with one thing in common.

The ever-incubating mass shooter, these young men nurturing their anger through first-person shooter games, violent pornography, through racism and a fascination with guns and violence, is our greatest, most stubborn and pressing threat — more so, I would argue, than Islamic terrorism or Russian hacking or immigration or trade wars.

America is in the throes of a decades-long epidemic that we have come to regard as we do AIDS or some forms of cancer, somehow tolerating it in our body politic rather than trying to solve it, or even address it.

Yes, we have a president who may be our angriest ever, who unleashes daily a fusillade of threats and name-calling and sexist remarks and racist dog whistles. But it would be facile to say Trump is the cause of this rage, which existed long before he got here, long before 9/11, long before the tech bubble or the Great Recession.

Wittingly or not, this collective anger is something Trump has tapped into and continues to ride, while the rest of us shout and argue over gun control or access to mental health or the culpability of parents and teachers. All of those things are relevant, of course, but they are not the cause. It is anger, stoked to malignancy by a culture in which it’s become acceptable to isolate yourself and talk, online only, to people who think and blame and rage like you do. And that way of life has somehow become almost normal.

Last week, the nation celebrated one of humanity’s greatest triumphs — the moon landing, something once commonly believed couldn’t be done. Perhaps our next moon shot should, paradoxically, be more earthbound: a collective dedication, from the White House on down, to figuring out why young men in the world’s greatest, most prosperous country are so goddamn angry.