Twenty years ago, as the 30th anniversary of the University of Texas Tower shootings loomed, Gary Lavergne completed an exacting account of the events that took place before, during and after Aug. 1, 1966. "Sniper in the Tower: The Charles Whitman Murders," published by the University of North Texas Press in 1997, has since appeared in paperback, mass market paperback and Kindle editions. We sat down with the unassuming Lavergne — by day, the UT head of admissions research, and the author of three other successful books — in his office on the ground floor of the Tower.

What prompted you to write about the Tower shootings?

I think it was late December 1994. I was watching a television program called "American Justice" and the episode was entitled "Mass Murder: America’s Growing Menace." About one-third of that episode was about the UT Tower tragedy of 1966. My sons were watching with me, and I told them that I was only 10 years old, but that I remembered when it happened, and how my father, who was the chief of police in my hometown, reacted. He had looked at the television and said, "This is not good. We are going to see more of this. That guy is showing every crook in the world what is possible."

What next?

Shortly after that broadcast, I looked for a detailed, responsible book about that incident and found out that none had ever been written. So I decided to write one. At the time, I had a job that required about 90 nights a year of hotel lodging. I wrote "Sniper in the Tower" in literally hundreds of hotel rooms over a three-year period.

How did you gain access to the detailed crime reports that inform your book?

Once I decided to write the book, I called the Austin Police Department and asked to see whatever documents and evidence they still had. I didn’t expect to see much, as the crime was nearly 30 years old. I was directed to the head of Robbery/Homicide, and we sat and talked. My dad was a cop, and I know a lot about how to talk to policemen. I volunteered information about myself and my academic qualifications. Then he grabbed a wad of keys and said, "Come on." We went to an evidence room vault, and there it was: three boxes labeled "Whitman." All of the APD, DPS and FBI reports as well as evidence like Whitman’s notes, diaries and the letters he wrote and left on the bodies of his mother and wife.

How did it feel holding the actual evidence from Aug. 1, 1966, in your hands?

It was kind of creepy at first. Then I got over it and began looking closely at things like his penmanship, the ink, the paper and how he folded it all. I found what he touched surprisingly informative. And, of course, there was the content of his writings — which is the true window on his thoughts and direction. I immediately recognized that it was more an expression of what he wanted me, as a reader, to believe, than what was really going through his mind — he was quite a manipulator.

What have you learned about the long-term impact of Whitman’s acts on survivors, witnesses and partisans?

I’ve written three true-crime books, and I am no longer surprised at how resilient this story is. Just today, only two days after the horrible shootings in Orlando, in which over 100 people were killed or wounded, I received six requests for television and radio interviews from news stations all over the country. Charles Whitman killed or wounded about 50 people, of which 17 died. Assume that each of those people came from families and friends that included dozens of people, and in one generation alone we are dealing with hundreds of innocent people traumatized by what he did. If you include witnesses, the affected population reaches into the thousands. Fifty years after this terrible event, I often hear from some people who cannot seem to let go of this story, and that makes me very sad — Whitman doesn’t deserve that much attention, and I find it difficult to believe the innocents who were killed or wounded, all of them wonderful people, would want us to live with such sadness every day.

Everybody seems to have an opinion on why he did it. Are there camps? Where do you fall?

In the beginning, I accepted the theory that a brain tumor triggered a seizure, of sorts, that overrode his ability to both control himself and discern the difference between right and wrong. After nearly three years of investigating and devouring everything I could find related to this case, I came to what was, for me, a very difficult conclusion: Charles Whitman was a cold and calculating murderer. We know, beyond not just reasonable but any doubt, what he did, and how and when he did it. For 48 hours before the sniping in the Tower there is no significant amount of time unaccounted for. Again, he could not have done what he did without controlled, thoughtful, serial decision-making in a correct order to accomplish a goal.

As FBI profiler John Douglas wrote, "His actions speak for themselves." Nothing he did appears undisciplined or random. He killed when he wanted to and behaved himself when he had to. He skillfully covered up his first two murders. Indeed, if a commando had been assigned to do the same thing, he would have assembled much the same arsenal, packed the same supplies and behaved in the same way. His notes about how he "doesn’t understand himself" and how he couldn’t "rationally" explain what he was about to do is the only thing he could write about himself to elicit sympathy. He could not have argued that he was innocent, or that it was an accident, or that he acted in self-defense.

You’ve written several other successful books, but this one, your first, still sticks with people. Why?

When tragedies like Virginia Tech, Orlando and Sandy Hook happen, I think we have a tendency to look to history for wisdom. Since Whitman was the first to "take his guns and go to school," and since it was the first public mass shooting of its kind, it becomes a place to start. James Alan Fox has said that it defined our modern concept of mass murder. That will never change.

There is also the Tower itself. It is iconic, recognizable, and literally the registered trademark of one of the finest universities in the world. It is everywhere UT is, and that is more than significant. Conversely, the Engineering Building where the Virginia Tech shootings happened, Norris Hall, is just not that memorable. People old enough to remember when this happened 50 years ago remember the Tower as well.

It is not like the McDonald’s in San Ysidro or the Luby’s in Killeen, where the body counts were even higher. There is also the image of Charles Whitman as a "blond, blue-eyed, all-American Boy." While on my book tour for "Sniper," in dozens of bookstores people my age walking by did double-takes at the cover. What they were looking at was Whitman’s picture — they remember him as someone from their past.

I don’t think ugly murderers like Richard Speck and Kenneth Allen McDuff get these second looks — they looked like murderers. The story often gets caught up in some of the most salient issues of our time: drug abuse, domestic violence, gun control, mental health, possible organic causes of violence and a number of other causes that many of us care deeply about. For example, during Texas’ recent debates over concealed and campus carry laws, I was approached by advocates of both sides who sought to use the Tower tragedy as an example to support their cause. (I stayed out of that.) Those who don’t like spanking, for example, use Whitman’s father’s brutal discipline as a culprit. The Texas Pharmacy Board made much of his abuse of Dexedrine. And so it goes with a number of other laudable causes in which Whitman does not serve well as a poster boy.

You actually work in the UT Tower. Does that change the way you think about that day 50 years ago?

"Sniper in the Tower" was released in 1997, and that was three years before I got a job at the university. At the time I researched and wrote the book, I had no close friends at UT nor was I otherwise affiliated with the university. I’ve worked in the same suite of offices on the ground floor of the Tower now for the past 16 years. It is an awesome place. I spend my time in a place that hands out some of the most valuable and precious assets that can be given to young people — the promise of a bright future and the hope that their lives will be made better. During the 2013-14 academic years, UT awarded nearly 14,000 diplomas. For the vast majority of graduates, the journey started in the office where I work. I often think about how those young people will go out and make the world better for all of us. And while I’m doing that, I don’t spend a lot of time thinking about Charles Whitman.