It's easy to prevent future mass shootings: We just need to spend a couple billion dollars hiring more security guards, installing alarm systems, metal detectors, and bulletproof glass, while undertaking a broad cultural shift toward reflexively reporting sad loners to the authorities.

That's the flawed thinking of a number of commentators—ostensibly on the right—including The Washington Examiner's Tom Rogan, The Washington Post's Jennifer Rubin, and of course, President Donald Trump, who tweeted in response to the Parkland, Florida, mass shooting:

So many signs that the Florida shooter was mentally disturbed, even expelled from school for bad and erratic behavior. Neighbors and classmates knew he was a big problem. Must always report such instances to authorities, again and again! — Donald J. Trump (@realDonaldTrump) February 15, 2018

Trump's sentiments were echoed by countless cable news pundits, politicians, and law enforcement officers. National Review's David French made perhaps the best case for an increased nation-wide emphasis on see something, please for the love of God say something. He wrote: "Looking at the deadliest mass shootings since Columbine, we see that the warning signs were there, time and again. People could have made a difference."

The warning signs always seem obvious in retrospect. Suspected Parkland shooter Nicholas Cruz appears to have been a gun-obsessed loner with disciplinary issues and a long history of threatening behavior, to the extent that other kids at Marjory Stoneman Douglas High School had previously joked about him going on some kind of rampage.

But there are a whole lot of weird teenagers out there, and the vast majority of them never hurt anybody. Reflexively reporting suspicious people to the authorities would create major headaches for everyone. A useful comparison might be the world of raising children, where the helicopter parenting has created a bunch of nosy neighbors. Busybodies routinely call the cops on parents who innocently leave their kids in the car for just a few minutes, or let them play in the park by themselves, or leave them home alone for too long. There are consequences to a see-something-say-something mindset that makes people feel obligated to report potentially dangerous situations to the police: parents go to jail, lose custody of their kids, and must jump through insane hoops to satisfy child protective services.

Does this approach make children safer? Certainly there are cases where a kid was spared a terrible fate because a bystander spoke up. But we can't pretend there are zero tradeoffs, or that the tradeoffs are automatically worth it.

Nor is just throwing more money at the problem much of a solution, despite what we hear from pundits. On Chris Hayes' show on MSNBC last night, Rubin lent support to the just-spend-more-money theory, saying:

If Republicans don`t want to do something about guns, why aren't they doing something about school safety? Why are we wasting money in all quadrants and why are we hollowing out all sorts of things that could be done at the state and local level, rather than persecuting so-called sanctuary cities, what about giving grants so that we can help to secure schools, that we can put in safety glass, that we can put in buzz in and buzz out systems…. I want to make sure we have enough money to put a cop in every school, to have safety glass in every school, to have an alarm system in every school, to have training for teachers. Why don`t we do that with $30 million rather than having a parade of the army to please Donald Trump?

Certainly any public expenditure sounds reasonable when judged against Trump's proposed military parade. But increased funding for school security wouldn't magically make students safe from mass shooters. There isn't even compelling evidence that metal detectors actually improve school security, and while security guards can break up fights between students, it's difficult to imagine that they would make the preplanned mass shooting a thing of the past.

Nevertheless, in an op-ed for The Examiner, Rogan claimed that $10.7 billion dollars is all we would need to "dramatically reduce the threat of school shootings." (If you believe that, I know a Nigerian prince you should meet.) According to Rogan:

I calculate $10.7 billion based on government statistics which estimate the total number of K-12 public schools at around 99,000 and post-secondary education facilities at around 8,000. That gives 107,000 total. Multiply 107,000 by 100,000 (two security guards each making $50,000 a year) and you get $10.7 billion. I believe $50,000 is a good total estimate for the average security guard salary when taking into account state-level variations in average wage. Why two guards and not one? Because with two trained, armed guards in every school, there would be strength in numbers with which to respond to a shooting incident. It's not just about the ability to dominate an attacker in the earliest moments of his or her attempted atrocity. It's that security officers could identify the sound or other signs of gunshots more easily than students or staff, thus enabling a quicker police response. They could also position themselves near to the various entry points of a school, preventing the kind of attack that we saw yesterday. To be sure, it's not a perfect solution. A gunman could still kill students before being isolated and neutralized.

Indeed, that's exactly what happened at Stoneman Douglas High. The school resource officer—the law enforcement agent who works in the school—wasn't able to stop the shooter from killing people. Would even more guards make a difference? We don't know that they would, but we do know that the 50 million public school students in the U.S. would attend school in a very different environment. At what point do we say that making kids feel like prison inmates isn't worth it? Rogan ignores this concern—"Nor do I believe that armed guards would intimidate students"—even though there is plenty of reason to think that the increased prevalence of cops in schools over the past two decades has negatively impacted students' civil liberties and due process rights.

Conservatives are right to be skeptical that changing gun laws would automatically produce some significant decrease in mass shootings. Skepticism about security increases is similarly merited. If we're going to compromise teen autonomy, raise suspicions, and give the authorities more reason to intervene in people's lives, we have to be sure that what we're doing is actually going to save a significant number of lives. Such evidence is in short supply.