John Wilkes Booth was just 26 when he killed Abraham Lincoln. Leon Czolgosz was 28 when he killed President McKinley.

And Lee Harvey Oswald was 24 when he killed JFK.

It's a scary pattern. Throughout history, there have been more than two dozen assassination attempts on the president of the United States. Four have been successful. And in three out of those four, the killer was a young white male in his 20s.

It was one of the first things I noticed when I started researching presidential deaths. And why was I researching that? I write thrillers for a living. My new one is about a serial killer who's meticulously re-creating the crimes of all the presidential assassins, from John Wilkes Booth to Lee Harvey Oswald. In the book, all four assassins are working together for the same secret cause. I write fiction. I made that part up. But as I was researching the novel, I spent two years looking into the commonalities of the people who try to kill a president.

To be clear, when you look at all assassins, as the Secret Service will tell you, there really isn't a single pattern. Potential killers are old, young, rich, poor … and from just about every background. But when you look at just the four assassins who were successful, the real pattern emerges (and yes, of course that's because it's a much smaller group).

Still, here's what the four assassins have in common: All four were surprisingly … and almost outrageously … neat. None of them did drugs. They weren't big drinkers. And among the four, they were barely identified as troublemakers, until of course that moment where they pulled the trigger. Most interesting to me: three out of the four were men in their 20s.

Beyond that, each one made their plan for weeks. And of course, they all had an abundance of two things: Patience. And luck. On top of that, when you looked at them all at once, the one thing they had most in common was simply this: All four were almost delusional in the belief of their cause.

When it comes to assassins, they tend to be divided into two categories: howlers and hunters. Howlers threaten us by calling in bomb threats and threatening to kill us, but the good news is, they rarely take action. For them, howling and making noise is enough. Hunters are different. Hunters act on it. They plot, plan, and execute. But here's what's fascinating: Howlers aren't interested in hunting. And hunters aren't interested in howling. Needless to say, from John Wilkes Booth to Lee Harvey Oswald, all four assassins were hunters.

It's that final detail that hit home as I think about the shooting of Gabby Giffords and the other victims of Jared Lee Loughner. So many of us reacted by saying, "What is the world coming to?" But as I look at it, I can't help but see something sickeningly familiar - an animal that's sadly become part of the American experience. Yes, there's a huge difference between the security surrounding the innocents near a supermarket and those protecting a sitting President. But quiet, young, 20-year-old sociopaths who keep to themselves … and are almost delusional in their self-importance and need to prove their cause through violence. As I saw Gabby Giffords testifying before the Senate last month, I couldn't help but think that the recurring profile has been haunting us for well over a century.

So where does that leave us? I found part of the answer last week, at a booksigning I was doing Connecticut. I was told by the organizers that some of the teachers from the Newtown schools would be in attendance. Knowing that, we made sure to get them free copies of the books I wrote for my own children: "Heroes For My Son" and "Heroes For My Daughter," collections of real heroes from Rosa Parks to Jim Henson to Amelia Earhart. Included in the book is one of my own heroes: my ninth grade English teacher. Even beyond Connecticut, we are a nation starving for heroes, and my hope was to share a few of my own to give the teachers extra strength and remind them of the power of ordinary citizens.

Sure enough, a small, dark-haired woman approaches my table and says she's from Newtown. For her, I had just one question: How is everyone doing?

Of course, she gave me what has become an almost standard answer in any tragedy: "It's hard." It's hard for the families burying children … and for the teachers who lost their students and colleagues … and even for the law enforcement folks who were first on scene.

But what struck me most was when she told me how close the community of Newtown had become. In this horror, it'd be so easy to isolate yourself and pull away. Instead she described a community that was closer than ever. Stronger than ever. A community that would get through this.

At this point, we are sadly almost growing accustomed to the recurring reports of senseless violence. And if I can take one lesson from it - and from all of history, be it from Ford's Theatre, to the book depository in Dallas - to a supermarket parking lot - those moments may knock us down, but they will never knock us out.

Brad Meltzer's new book, "The Fifth Assassin," is about a serial killer who's recreating the crimes of all the presidential assassins, from John Wilkes Booth to Lee Harvey Oswald. He's also the TV host of "Brad Meltzer's Decoded" on the History channel. Find more about him and contact him online at