Editor’s Note: David Eagleman directs the Center for Science and Law and is an adjunct professor of neuroscience at Stanford University. He is the writer and presenter of the PBS series, “The Brain with David Eagleman,” and the author of the New York Times bestseller, “Incognito: The Secret Lives of the Brain.” The opinions expressed in this commentary are his own.

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Stephen Paddock's brother has speculated, "something went wrong in his head." David Eagleman asks, what precisely was it?

We know little about Paddock but quite a bit about biological factors that can be associated with violent behavior, Eagleman says

CNN  — 

In the wake of the mass shooting in Las Vegas, Stephen Paddock’s brother Eric speculated, “something went wrong in his head.” But what precisely was it?

It’s easy to chalk up Paddock’s horrific actions simply to “evil,” as politicians and media are inclined to do.

But if it’s possible to gain insight into his actions at a biological level, we might be in a better position to fend off such tragedies in the future.

David Eagleman

In the case of Paddock, there is shockingly little data on who he was, so diagnosis at a distance is impossible. Nonetheless, we can focus on some important facts to clarify the space of possibilities.

First, several people have suggested online that Paddock is a “psycho.” It’s important to note that technically there is no such word. A person might be psychotic (e.g. with schizophrenia, which is a disorder of cognition), or they may be psychopathic (someone who doesn’t care about others). Either could be considered here, so we’ll turn to these first.

Paddock was almost certainly not schizophrenic. As far as we can tell he had no history of schizophrenia, and besides that, he was 64 years old. Schizophrenia is a young person’s disorder, usually surfacing during the late teens or early twenties.

Could he have been a psychopath (also known as a sociopath)? Possibly. His father, Benjamin Hoskins Paddock, a bank robber, is claimed to have been a psychopath (I have no real evidence of that diagnosis beyond the news reports). Psychopathy is heritable, at least in part, as revealed by analysis of identical twins – however, keep in mind that most mental issues are a combination of nature and nurture.

The fact that Paddock was divorced twice is certainly consonant with psychopathy; strings of broken relationships are typical among psychopaths. However, the rest of the data about him is too thin to insist on psychopathy.

In fact, people who knew Paddock (for example, his brother and his neighbors) seemed shocked by what happened. His brother claimed that Paddock recently sent a walker and boxes of cookies to their mother – not typical of psychopathic behavior. Finally, most psychopaths use people to get what they want; it’s not clear that psychopathy alone would explain a murderous rampage on a crowd of strangers.

This leads us to the second issue. Is it possible that there were changes in Paddock’s brain, such as a growing tumor? This is always a question that needs to be considered, especially as there was apparently little about Paddock that foreshadowed this monstrous act. Las Vegas police said they had not previously even known his name.

“There’s absolutely no way I could conceive that my brother would shoot a bunch of people that he didn’t know,” his brother Eric said. “Something just incredibly wrong happened to my brother.”

Some readers will remember the University of Texas Tower Sniper, Charles Whitman, who killed 16 people in Austin just over half a century ago. At autopsy, Whitman was discovered to have a tumor pressing against a part of his brain called the amygdala, which is involved in fear and aggression. Is it possible that a similar pathology was happening in Paddock’s brain? Although the likelihood of tumors is low in general, the hypothesis cannot be ruled out until autopsy.

It is important to note that a tumor isn’t the only thing that can cause such changes in behavior: strokes or a traumatic brain injury can do the same. And one disorder in particular deserves mention: frontotemporal lobar degeneration (FTLD). Although the name is long, this simply refers to a deterioration of two lobes of the brain, the frontal and the temporal: two regions that underpin much of the decision-making and emotion that makes us social creatures.

As these brain areas degrade, people develop frontotemporal dementia (FTD) – and this often comes hand-in-hand with violent, asocial behavior. When I heard Paddock’s age, I immediately began to wonder about this, as the onset of the disease is typically in a person’s late 50s.

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    Patients with FTD often display altered moral feelings, diminished empathy and disinhibited behavior. Among other things, it affects a part of the brain known as the ventromedial prefrontal cortex, one of the key areas involved in moral emotions about others. Damage to that area is sometimes referred to in the medical literature as an “acquired psychopathy.”

    Did his girlfriend or neighbors notice any changes that would be consistent with these possibilities?

    Finally, we can’t rule out the possibility that Paddock’s erratic behavior resulted from some nefarious combination of problems: for example, there’s no reason one cannot be psychopathic, take drugs, alcohol, or medications, and have FTD as well.

    It is impossible at this point to attempt anything beyond conjecture. However, as Stephen Paddock’s relationships are plumbed and his medical records are scrutinized, these are some of the paths for examination. And if his self-inflicted gunshot did not damage his brain too badly, the next logical stage will be an autopsy – and there we might finally gain deeper answers.