The image is burned into my brain. It was 1981. The man is wearing a three-piece suit. He has a mustache and he’s wearing brown shoes; everything about him screams, “Late ’70s, early ’80s.” He is wearing an enormous ring on one hand, which might be a class ring or might be something specific to the Secret Service. He is guarding President Ronald Reagan. He is standing on a sidewalk in Washington, D.C.; he is one of many in a milling, agitated crowd.

He is holding an Uzi submachine gun.

I first saw a picture of this agent years ago, while reading a compendium on handguns. The section on the Uzi featured the image. The picture was taken after John Hinckley Jr. was tackled, for he had just shot President Reagan, Press Secretary James Brady, a Wasington, D.C., police officer named Thomas Delahanty and Secret Service Agent Timothy McCarthy. The round that injured Reagan was reportedly a ricochet from the President’s own armored limousine. While Reagan would make a full recovery, Delahanty retired. James Brady was permanently disabled. History was made.

The imagery sticks with me because it is a sight to which we in America are unaccustomed: a man with a submachine gun in plain view on a public street. It is imagery that quickly, simply and efficiently conveys foreboding and alarm. We see an image like that and we wonder when the next such shooting may occur. We marvel at the seemingly random nature of such horrors. We fret over what may endanger our families and ourselves. What we don’t stop to think about these historic and iconic acts of desperation is that they are less likely to occur without some advance notice. By this I mean that, had the Internet existed in 1981, Reagan’s would-be killer might well have revealed himself before the shooting.

Hinckley was, to put it bluntly, nuts. He was obsessed with the movie “Taxi Driver” and was more or less stalking actress Jodie Foster. He sent Foster mail and was, from all reports, fairly high-profile in his madness. Long before he tried to kill Reagan – ironically, imitating a movie character who was himself mentally disturbed – there was every reason for the people around Hinckley to believe he was capable of such an act. Is there any doubt that someone like that, were he just getting started today, would be posting to Jodie Foster fan sites, commenting on the movie’s Internet Movie Database page, and erecting creepy Facebook pages devoted to the objects of his obsessions?

Jared Loughner, the infamous Arizona shooter, wrote online of various issues he had. There was no doubt to anyone reading those posts that he was emotionally disturbed. Seung-Hui Cho, the Virginia Tech murderer, was enamored of popular entertainment and disturbing movies like “Oldboy”; he took pictures of himself posing with a hammer, after the fashion of that film’s protagonist. And then there was “Gunkid,” born John Melvin Davis – a felon who holds the distinction of being, perhaps, the most infamous and prolific Internet troll ever to post online. “Gunkid” was sent to prison for possession of firearms and ammunition after breaking such laws previously. He was notorious for the outrageous things he wrote about guns, their applications, and his own ownership and use of them. He wrote ridiculous things, advocating methods that were unworkable, encouraging behavior that was actually dangerous. If he’s not in prison right now, you can bet he’s posting similar nonsense online under any of several tens of aliases.

Except for the fact that Gunkid was more dedicated than most, trolls like him – the term “troll” applies to those who post and/or lie online to disrupt others’ discussions and to gain attention for themselves – abound on the network of networks that is the Web. Some use the Web to make ominous statements presaging there coming violence. Others suffer from personality disorders like NPD, defined as “a condition in which people have an inflated sense of self-importance and an extreme preoccupation with themselves.” What all trolls have in common is that they use the Web as a stage, on which they present themselves however they wish to be seen. It is the equivalent of walking into a crowded room and shouting “Look at me!” We will probably look; we may not take what we see seriously.

We ought to pay attention.

People who exhibit signs of mental instability … well, they exhibit signs of being mentally unstable. All you have to do is pay attention to what they do and say. If they strike you as a little off, as possibly dangerous and as obsessed with the attention they get online for acting this way, they just might be deeply disturbed. If we dismiss them, if we make excuses for them, if we give them the benefit of the doubt – we just may regret it.

I once watched an interview with a historian who remarked on Hitler’s “Mein Kampf.” The title is generally translated to mean “My Struggle,” and in his book, Hitler was pretty damned clear about what he believed and what he intended to do. The many Germans subsequently shocked and stunned by revelations concerning Hitler’s death camps (setting aside Hitler’s self-destructive impulse to dominate the world) might have been a little less surprised if they’d actually bothered to read what Hitler wrote. I don’t mean to affirm Godwin’s Law in invoking Hitler’s name as part of this argument, but the implications are obvious. You ignore the acting out of people who are obviously, demonstrably strange at your peril and to your detriment.

Each of us has seen viral videos featuring people who are obviously a little cracked. Be they narcissists or simply weirdos, all of us can think of someone who just might be dangerous. What ALL of those people will likely do, frequently on the Internet, is tell us what they think and how they feel. They are themselves the best predictors of their crimes.

We should listen. We should act.

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