As the world knows, Trayvon Martin was stalked and shot to death by an armed vigilante. The police report that night called it an unnecessary killing to prevent unlawful act.

We will never know the full story because the victim has been forever silenced. That's the thing about guns, they have the last word.

Martin's killer George Zimmerman pleaded self-defense and was acquitted thanks, in part, to Florida's Stand Your Ground law. That law was the handiwork of the national rifle association, whose lobbyist, Marion Hammer, is seen standing there beside Governor Jeb Bush when he signed it In 2005.

Ever since, members of the right-wing organization, the American Legislative Exchange Council, also known as ALEC, have been pushing versions of bills like it in state capitols across the country. Twenty-one states have followed suit.

To understand what's happening, read this important new book, The Last Gun: How Changes in the Gun Industry Are Killing Americans and What It Will Take to Stop It.

The author is Tom Diaz. He’s a veteran, former N.R.A member, and worked as an assistant managing editor at the conservative Washington Times. Trained as a lawyer he served as a senior policy analyst at the Violence Policy Center before turning to full-time writing and speaking on guns and their impact on America.

Tom Diaz, welcome.

TOM DIAZ: Thank you so much.

BILL MOYERS: I heard you say earlier that the real winners in the Florida tragedy are the NRA and the gun industry. How so?

TOM DIAZ: Well, for two reasons, I think. One, it, in their eyes validates the whole concept of this, what they call Stand Your Ground law. Look, Zimmerman stood his ground and nothing bad happened to him, so that validates the idea that you're going to need these things to protect yourself. Secondly, it increases the market which is what ultimately this is all about. Now they have a case to say, don't you wish you had one of these things in your pocket if some guy was beating your head in the sidewalk? So, one hand reinforces the other.

BILL MOYERS: The conservatives are claiming that Stand Your Ground was not a factor in this case. The "National Review Online” says the media is quote, "inventing reasons to blame the verdict on Florida's gun laws,” when in fact the Stand Your Ground law wasn't even used in Zimmerman's defense.

TOM DIAZ: It wasn't used technically, that I would agree with. But the Stand Your Ground law changed the circumstances in Florida, under which a person might go about armed as did Zimmerman. And so that even if the lawyers, I think quite wisely the defense lawyers, chose not to make this an issue, it encouraged the kind of carrying of weapons and the thought that, well, I can use this. The law of self-defense which goes back to ancient times to the Talmud, it's absolutely clear that a person who's being threatened, whose own life is being threatened as the right, the moral, ethical, legal right to if necessary kill a person trying to kill them, that's not a question.

What we did develop though in our common law were restraints about when you might use that. One had a duty to retreat generally, avoid violence if you can. Why take another human life if there's a way out of the conflict? There was an exception to that, and that was in one's own home. This is the so-called Castle doctrine. That's where the word, the phrase, stand your ground, came into legal significance.

If you're in your own home and I come in and clearly are going to do you harm, you have no duty to retreat. If necessary you can take my life. What's happened here is that the NRA, Marion Hammer, and the people in Florida and gun advocates generally have twisted this language so that now they've taken this concept of stand your ground into the public space. And they've tried to say, well, the law hasn't changed. In fact the law has changed. It was very carefully crafted to reduce mayhem, to reduce the chance that somebody's going to be killed and now turned into a situation that practically begs for someone to be killed if I feel threatened.

BILL MOYERS: Do you think this is what happened to George Zimmerman?

TOM DIAZ: Yes, I have to say I don't think George Zimmerman is a victim, I think he was a tool.

BILL MOYERS: A tool?

TOM DIAZ: He was the perfect marketing target of the gun industry, small handgun carried around, if you're going to buy, no pun intended, at Target, which was apparently his destination, don't you need your gun to protect yourself? This is exactly what the NRA and the gun industry want to do because it increases sales. And there's a whole, within the industry themselves they talk about how wonderful this concealed carry, Stand Your Ground laws are for selling small handguns exactly like Zimmerman had.

BILL MOYERS: But there are dangerous people out there, they will tell you that.

TOM DIAZ: We have known there are dangerous people since medieval times. And we've understood there's a problem. And we've said you can defend yourself when necessary. That hasn't changed one bit. What has changed is the mix so that we now have people going around with more deadly weapons.

It's something that I think that most average Americans simply have no understanding of the mindset of the diminishing number of people who own firearms and who own them specifically to carry out on the street, nevertheless they have a mindset. And that mindset is danger lurks everywhere and you better have your gun to protect yourself.

Goes to the extreme of having, you need a gun in your bathroom because what if you're going to the bathroom and your gun is in the living room. You need a gun in your ankle because suppose your drop your gun that you carry in your waist. This is not an exaggeration. I read regularly the fan magazines of the gun business. And it's, I say it's like reading these bodice-ripper romance novels without any good parts.

The two things they talk about more than anything else are military style assault rifles and handguns for self-defense. Almost every issue of every magazine fuels this feeling that you better have a gun, and hey, here's the greatest new gun in the industry.

BILL MOYERS: You're saying this is a business strategy?

TOM DIAZ: Oh yeah, the gun industry admits it. One of the prolific writers in the industry magazine, this is not fan magazines now. This is a magazine where the industry talks to itself, called it cashing in. Basically, I'm paraphrasing here, but, the exact phrase, but he said if you're not cashing in on concealed carry laws, you're not going to make money.

Article after article in the industry publication says these laws are going to boost your sales of handguns and specific kinds of handguns that are going to bring you out of the slump. And not only that, both in the case of assault rifles and handguns one writer described the customer as a walking cluster, a walking cluster of after-market sales.

You're going to need special holsters. Now they're even saying you're going to need a special coat for the winter or the summer to conceal your gun. So the after-market and accessories are where, and as a matter of fact, it's where, as in a lot of consumer products, it's where the big profits are.

And what it appears to be is that it's not so many new buyers as it is old buyers buying more and more guns. The average number of guns owned by gun owners has gone up and up and up. The average number of households and individuals who say they own guns has been going down. So what we have is fewer and fewer people buying more and more guns.

BILL MOYERS: How do you reconcile what you've just said about fewer and fewer people actually owning guns with the increasing power of the National Rifle Association? You write in your book that the NRA has gone to extreme lengths to draw a veil of secrecy over the facts, the facts surrounding its impact, on our lives.

TOM DIAZ: Well, the gun industry learned a lot from the cigarette industry. When the cigarette industry was sued one of the things, probably the most important thing that people who litigated against the cigarette industry, was the internal papers of the cigarette industry where we found out these guys not only knew they were killing people, they went to lengths to cover up the fact the they were killing people.

The gun industry was terrified when some litigators said, hey, why don't we do to the gun industry what we did to the cigarette industry and other evil industries? So they got Congress to pass a law do away with lawsuits again, it's very hard to sue the gun industry. But there were two other corollaries that led up to that.

One was preventing the Centers for Disease Control which is our public health research arm, the source of almost all of our data about everything from measles to firearms death, they decided, a congressman by the name of Jay Dickey said, hey, we don't want them doing this research on guns. He originally wanted to shut down the whole unit that does all research. And finally they compromised and said, okay, you just can't spend any money on guns.

So we have told the only national public health research agency, you can look at anything else. You can look at measles, you can look at workplace accidents, but don't look at guns. So that's one. Number two, there's an agency a law enforcement agency, a federal law enforcement agency called the Bureau of Alcohol, Tobacco, Firearms and Explosives. I'll call it ATF. ATF does something, it’s called tracing crime guns, which means if a gun is used in a crime or is found at a crime scene or illegally possessed, they trace that gun from its manufacturer, because Federal records are, the manufacturers are required to keep records, to the fist point of its public sale.

And then if they can they follow it to the point which it was either found or used in a crime. The value of that in terms of law enforcement is law enforcement investigators can tell was this gun used in another crime or crimes, how did this person get the gun, was it possibly sold by gun traffickers?

From a public health point of view the value of this data, and we're talking about millions upon millions of cases investigated, that is, traced, by ATF, is that we can answer some of the questions that now are just veiled. For example, when I worked in this field people would call me and say, well, how many Glock pistols were used in shootings in the last ten years? And I would say, nobody knows. And we don't know.

We could know if we could access the ATF database. The same thing when the horrible shooting in Newtown, people would say, well, how many of these Bushmaster AR-15 assault rifles have been used in shootings or crimes? We only know anecdotally. But if we could get that ATF data we would know precisely. So it would answer questions about do these designs make a difference? Are specific kinds of guns implicated in crime?

So that's the ATF contribution. If you take those two together, public health, law enforcement, you have a very good picture of what is the impact not only of guns generally in the United States, but of specific types, calibers, manufacturers. The industry is terrified of this.

BILL MOYERS: How is it they've kept Congress from giving us that basic information? How do you explain the power of the industry over our political process? They own our political process now.

TOM DIAZ: Well, I think there are two answers to that. And it doesn't give me any joy to say it. One, the, one of the things the NRA has a program called Refuse To Be A Victim. The American, certainly the American national, and I'll say liberal, progressive, whatever you want to say, political establishment has chosen to be a victim.

They have given up on guns. They've bought into a thing called the third way which is somehow there's this mythical common ground we can reach with the NRA or the gun industry, and let's not talk about gun control. They call it the third rail of politics, so you have a victim here. On the other hand it must be said that the National Rifle Association has what every politician wishes they had, that is they have somebody in every congressional district.

Even if it's only one or two people they have somebody. When Wayne LaPierre in his palatial headquarters in Fairfax, Virginia pushes the button, the talking points go out, the phones or the emails arrive in Congress. The other side is not that organized. People who are gun control advocates have typically been small groups in Los Angeles, Washington, New York. They can't respond to that. That I hope, I think is changing.

BILL MOYERS: Tom, we're out of time right now, but let's continue this discussion online.

TOM DIAZ: Great, thank you.

BILL MOYERS: The book is The Last Gun: How Changes in the Gun Industry are Killing Americans and What It Will Take to Stop It. Tom Diaz, thanks for joining me.

TOM DIAZ: My pleasure, thank you.