SOUTH FREEPORT — For years, I have startled people in my office by asking a simple question: “If you got hit by a Mack truck outside my office, would it matter whether you were run down deliberately or whether the truck’s brakes failed? Would your injuries be any different?”

In therapy, the question is not as simple as it looks. Motivation matters hugely when forgiveness and understanding are the goals. But no matter how much we come to empathize with or understand the psychological “truck drivers” that wound us, we carry the wounds. Motivation and intent can change neither broken bones nor broken souls.

As I reflect on yet one more senseless mass murder, I pose the same question. What does it matter “why” the Las Vegas gunman killed 58 people and wounded hundreds more earlier this month? Whatever answer we find will neither prevent those deaths, nor restore those compromised lives. Why are we so focused on knowing why?

After Sandy Hook, I spent three months reviewing hundreds of pages of documents and reports, every analysis I could get my hands on about that senseless killing of children. As a psychologist, I wanted to understand why Adam Lanza’s pain and suffering led to such a horrific act. I lived inside his head, and I learned a lot. There were multiple failures: of parental judgment, of educational intervention and of psychological treatment. Everyone failed this severely impaired autistic young man, and we all paid a price.

I still think about every juncture where better choices could have been made. I want to remember them, to learn from them in my practice and to advocate for them in the world.

But there is no scenario I can envision in which I would have felt safe with Adam Lanza having access to an armory of high-powered weapons. For all the clinical errors that were made in this young man’s care, the public health failure was a simple one. No one had the courage or common sense to restrict his access to guns.

I know why I am fascinated by the “why” of gun violence. It’s my profession. It’s my need to understand human behavior. “Why” will always be a psychologist’s question.

But when the media and the gun lobby and the National Rifle Association keep talking about “why,” it is a distraction. They do not want us to look at these shootings as public health emergencies. But they are. And the public health question is not “why.” It is “how.” How do we reduce them? How do we stop the carnage on our streets?

We will never prevent every mentally ill person from being a threat. We will never prevent every gun enthusiast with delusions of grandeur from tripping some internal switch that sets off a killing spree. But if we confuse psychological motivation with public safety, we distract from what is truly important. We head down the rabbit hole of understanding one broken mind, and miss the broken system that does not protect us.

So, the next time someone asks me, “Why would someone do this?” my answer will be different. I will tell them it does not matter. Understanding individual psychopathology misses the mark. It will never solve the problem. What matters is how we have created a system in which the protection of all of us matters so little.

Let’s leave the psychological autopsies to others and see this for what it is: a public health crisis that puts ordinary citizens in danger every day. Let’s focus on the “how.” How do we reduce the chances of gun violence happening over and over and over again? The same way we stop the Mack truck driver’s brakes from failing: by setting standards, and requiring inspections, and regulating drivers.

Guns are what kill us. Guns: unregulated, unrestricted and uncontrolled. If we are not willing to admit that, we will never change it.