Today on radio, Glenn invited author Brad Meltzer onto the program to discuss his new book The Fifth Assassin. While the book is fictional, Meltzer did extensive research into the history of assassinations and assassination attempts throughout history and found some startling connections between them. He also spoke with former President George H.W. Bush about what it was like to live knowing that there were people out there who want to see you dead. Listen to the revealing conversation HERE and check out The Fifth Assassin HERE.

Rough transcript of the interview is below: 

GLENN: Brad Meltzer is a good friend of the program. He's a "New York Times" best-selling author. He's the host of the show on The History Channel decoded. He has numerous best-selling books. His new book is called "The Fifth Assassin" and he actually picks up something that I'm really intrigued about and that is and I wish more people knew. The assassins of presidents in the past have a lot in common a lot in common. And his new book is what if they not had a lot in common, what if they were all working towards sort of the same goal. Brad is here to explain, and tell us about his new book.

VOICE: Thank you pal.

GLENN: Tell me the theory of your new book.

VOICE: You hit it on the head. I started with a guy coming to me, and he said Brad, I work at a museum in Washington D.C. that almost nobody knows about, and you've got to see what we have here. I get all these crazy letters from people all the time from people who see the TV program and just tell me what you have. And I have pieces of Abraham Lincoln's skull, and I have the bone of the John Wickes booth and I have actually the bullet that killed Abraham Lincoln. Would you like to see it? And the government has these things. He didn't have artifacts from the Lincoln assassinations. He had the other assassinations as well. And it got me to thinking what do these assassins have in common and that's the topic it's a serial killer is meticulously re-creating all of the assassinations of all of the past presidents from John Wickes booth to Lee Harvey Oswald and wants to be "The Fifth Assassin". That's the plot but the theory is what they do have in common, when you look at the assassins. The Secret Service did a study, if you look at all of the assassins who have killed a President they basically have nothing in common. They basically have every social economic background. They're young and old. If you look at the four that did kill a President it's amazing. None of them did drugs. They weren't big drinkers. All four were surprisingly and outrageously neat and none of them except when they pulled that trigger was identified as a troublemaker. And what's interesting to me three out of the four of them were in their 20s. But beyond that they were all kind -- these are the two things I couldn't shake is one thing they had in common they were all for men with a cause. And we all know the power of that. But when it comes to assassins they can be divided into two categories. Howlers and hunters. And the howlers will send scary notes and there's a bomb threat but the good news is they rarely follow through. They just want attention so howling enough noise is enough for them. It's different with hunters though. Hunters actually research and prepare, and plot and follow that path to a goal. Howlers though, aren't interested in hunting and hunters aren't interested howling. And needless to say from John Wilkes Booth to Lee Harvey Oswald all four assassins were hunters.

GLENN: There's also the one thing they had in common too is a Socialist with the exception of Boothe, a Socialist or Communist agenda.

VOICE: Yes. It's very interesting. You know -- when you look at the background it's amazing. Sometimes -- listen I write these novels I make it up. We know that's half of the fun of it. But I'm researching these things and I'm going wait a minute, at the time when you look at McKinley there was a plot to murder the top seven leaders around the world, and then oh wait this is also true anarchists are also running around when you see not just McKinley's time but Garfield's time, and then you also see it with Lee Harvey Oswald. And wait a minute am I making this plot up for this book or is the plot already there and of course, you know it is amazing when you see those things in common.

GLENN: So George H. W. Bush helped you with this.

VOICE: He did. A couple of years ago HW 41 the dad who just got out of hospital wrote me best fan letters I ever got saying he loved my novels and would I sign a copy for him. And listen you're the President I'll send you a free book. You get a free book out of me.

GLENN: Wait wait wait. Not this President. Some presidents double, triple, quadruple.

VOICE: Yes. I see I cued that up for you. And he's helped me with three books now, and listen I can make whatever I want, and we all know there are a few people that really know what it's like to sit in the White House and know for sure that someone is out there that wants to kill you. I went to Bush, and I said to him what's it's like. And were you scared for those moments. And he said I wasn't really scared. And I kept going back to him, and saying were you scared when this happened? And he's always pretty forthright. He's at the age of 88 years old there's no bravado. He's like Brad I'm drawing a blank. I've been tense. Scared is easy. And it made me think that when you think of a construction worker out on the edge of a girder, you know the fear of heights on the skyscraper is not part of the job. I think that's how it is for many U.S. presidents. Even though that fear is there it's not part of the job. Those details that Bush gave me I put in my book. When you read it you think wait, that seems real. And that's why. Because I like to have that source there.

GLENN: In today's world where they're talking about gun control and everything else. Does it make you tense to write a book where you're talking about "The Fifth Assassin". I know that the President isn't the President in the book. You know what people will say.

VOICE: I've been working on this book for two years. Little did I know. For me it's amazing. When I heard about the shooting in aurora your Newton, Connecticut so many of Ussery act what does this world come to. When I looked at it I saw this part of animal that's been part of the American experience. But a quiet 20-year-old sociopath who keeps to themselves and almost delusional in their approach. Their profile has been haunting us for more than a century. We've been here for a century and a half.

GLENN: Tell me what you think. I think that the best fiction writers which I would put that in the category. The best ones that are ones that will tell you the truth what is possible. You're a fiction writer what do you care. You look at all these scenarios. What's feasible. I could tell a book about and people will by buy. What do you think happens next if the President does massive executive orders and starts to remove guns from our society? What do you think happens?

VOICE: What I worry putting aside the guns for a minute. I've spent two years how the Secret Service keeps the President safe. One of the persons said this flat out they do penetration testing. What they do there's people in the government who're hired to break into the Pentagon or doing it since World War II, and now we've taken to a new level. And he broke into the inauguration, and got underneath the President's seat where the President sits where the parade is. Forget about the guns issue right now. Think about how many hunters are out there. If it's that easy that it's happening. To be completely honest with you it scares me how easy it is. If you use history as your guide we have to learn something from these assassinations. It was until until Garfield went down that the Secret Service realized we;ve got to protect him. In the case of JFK every time you're trying to imagine a circle that's getting smaller, and smaller trying to protect him.

GLENN: Brad Meltzer called "The Fifth Assassin". You're in a real treat.

VOICE: I want to mention one thing to you. You and I talked about Camp David a while back. I loved this detail. Camp David is a real life service. Is that people know Camp David from accords and what they are. Camp David is a President's playground. They can go there and play golf, and skeet shoot and what they have there most important thing is no press, and so when Bill Clinton said his allergies prevented him from going there. But when he learned that the press was barred from there his allergies disappeared.

GLENN: I will tell you that with this President his hand in our pocket is preventing him from going to Camp David. It allows him to go to Hawaii.

VOICE: I know. It's a little more expensive than a helicopter ride to Camp David. I love Camp David, and finding out things. There are real secrets on the estates. I know you love the insider stuff. They go from where the Secret Service compound and go underneath. And I won't tell you where it comes out. In those details it's amazing when you think about the security.

GLENN: I would hope you change some of these details.

VOICE: I did change the change of security point.

GLENN: Let's not make this a how to book.

VOICE: I always try to change the security protocols. And the that the and that you people to read your book but not at the cost of our security. We always change the security protocol.

GLENN: Thank you Brad.