The deadliest murder-suicide in modern American history didn't actually occur on US soil. In the fall of 1978, more than 900 followers of deranged preacher Jim Jones—including roughly 300 infants and children, many of them people of color—perished after being ordered (or forced) to swallow a cyanide-laced drink in Guyana, South America. Many had sought an alternative existence defined by Jones's distinct vision of social justice, but their leader, whose brand was suffering amid myriad accusations of misconduct, was determined not to go out alone. That November, US congressman Leo Ryan and a coterie of journalists and family members visited the compound, and some cult members tried to leave with them.

Jones, perhaps sensing the end was near, unleashed mass death.

But history often seems to forget that the Peoples Temple, as Jones's notorious organization was formally known, did not begin as a morbid enterprise. Early in his career, in fact, Jones was a progressive (and successful) leader in the budding civil rights movement who some expected to seek elected office.

In his new book, The Road to Jonestown: Jim Jones and Peoples Temple, out Tuesday, investigative journalist Jeff Guinn—the author of the national best-seller Manson: The Life and Times of Charles Manson—traces the history of America's second-most infamous cult leader. From his early days as an idealistic Indianapolis minister to his almost rock star–esque descent into sex, drugs, and dubious acts of healing in California, to the alleged jungle paradise in Guyana, Jones was no ordinary grifter. We chatted with Guinn about how this man was once viewed as a sort of wannabe American Gandhi, how close he came to running for president, and what "don't drink the Kool-aid" really means.

Here's what he had to say.

VICE: I was fascinated by Jim Jones's early days as a young minister in Indianapolis. Can you talk about the kind of guy he was then, and whether there were any hints of his dark future?

Jeff Guinn: If we look at what Jim Jones became later in life, then there certainly are signs from his early childhood that this is somebody who is seriously off kilter in some ways. Even as a child, he was deceitful. He was manipulative. He was willing to do whatever he had to do to make himself the leader and have people follow his commands. Yet one of the most shocking things about Jim Jones is if you really study his life, if you go back and look hard at his formative years in 1940s and 1950s in Indianapolis, this man almost all by himself integrates the city—and this is years before there's civil rights laws making integration mandatory.

He built this reputation—that he eventually used to bring so many people to ruin and death—by accomplishing absolutely magnificent things. If Jim Jones had been hit by a car and killed somewhere toward the end of the 1950s, he'd be remembered today as one of the great leaders in the early civil rights movement, and he would have earned that reputation. That makes what happened to him even sadder and actually more tragic. He had the ability to do great things, and instead he used his talent for provocation, for manipulation, and as a result, he's remembered today as a terrible person. Frankly, he earned that.

How did Jim Jones blend the gospel and Marxism in his preaching, and why do you think this curious juxtaposition gained him followers?

Peoples Temple, as it grew, began to swell to thousands and thousands of members. It wasn't so much that every one of them was a member of Peoples Temple for the same reason—Jones was an expert at being something to one segment of his following and something [else] to another. He built his early ministry on both the Bible and trying to help his followers get some kind of social justice in this lifetime. It wasn't, S__ome day you'll go to heaven, and that's where the meek get everything they deserve. As his church grew, he began to try to use its membership to work for social change.

They became very politically active, very socially active, and there were people who joined him for that reason. They didn't particularly care about the religious end of things—they wanted to bring about change. Jones was a socialist, which first is a different thing from a Communist, but his main focus, what he would say the theme of Peoples Temple was, was to feed the hungry, clothe the naked, and try to set the kind of example where everyone has dignity, everyone has an opportunity. Peoples Temple was supposed to be a shining example, and the rest of the world, the thinking goes, would ultimately decide, We need to copy it.

He also would proclaim himself to be God and claim that he could do these miraculous healings, which were all staged. He got a percentage of people who followed him because they thought he was something more than human.

Was there a single moment where it all began to turn—to go bad? It seems like there was a long trail of misconduct on Jones's part. How did he pull that off for so long?

He was able to do it because he did it incrementally—it didn't happen all at once. He turned it up bit by bit by bit. One of his followers compared it to a frog in a pot of water, with the followers being the frog. If you drop a frog into a pot of boiling water, he automatically will try to jump out—he knows it's dangerous, he knows it's threatening to him. But if you put the frog in a pot of lukewarm water, with just a little heat underneath, then gradually turn up temperature, the frog stays until it's being boiled to death and only realizes then that it should have jumped.

Jones's followers initially were loyal to him because Peoples Temple was doing so many worthwhile things. They really were helping people who needed it, and only gradually does Jones start becoming the monster that he proves to be. Again, we tend to think that he must have been this way the whole time, which means everybody who followed him were brainless idiots. That is not the case. Right up until his last months of Jonestown, when the drugs and his own personal demons just sort of overtook him, Jones had the ability to impress virtually anyone he met as one of the finest, most public-spirited people around.

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How close was Jim Jones to becoming a real politician?

Once Jones is in California, he begins attracting followers who believe he is without flaw, [that] whatever Jim says must be right. He stops hearing from people, like, Hey, wait a minute, I think you're wrong about this. He's only told how brilliant he is, how wonderful. It's human nature to start believing it, and Jones was certainly more prone to that than any of us. He's removed from criticism, and that is a huge thing.

Just before all the public scandals broke in California that drove him to Guyana, Jones was starting to explore getting into politics. He was giving interviews and saying that he really couldn't run for office... yet. Maybe sometime soon. Remember Jim Jones was working as an equal behind the scene in California. He knows several senators and congressmen, and the governor, and he's thinking about getting into politics himself.

A man who's willing to think he might be God is not going to go small when it comes to public life. Jim Jones as president of the United States might seem ludicrous now, but ten years ago, would anyone have believed that Donald Trump could be president?

You've done your share of true-crime reporting, but this is a uniquely dark episode in American history. Did it weigh on you?

Writing the chapter about November 18, 1978, was the most difficult time I've ever had as a writer. I'm 66, and I've been doing this for close to half a century, and I've never experienced anything like this, because I got to know the people. Because I've been in that jungle myself, cut my way through it, knew what it meant to stand there in November at the height of the rainy season in the mud. It struck me it as a visceral thing, besides being an intellectual thing. I would write for a couple of hours, and then I'd just have to just walk away from it.

When I finished, it hurt me when I read it, because even with the first pages, I know what's going to happen. Not only what's going to happen, but why it's going to happen, and I care about the people that it's going to happen to. I hope for the people that read this book that they understand the Peoples Temple and Jim Jones better. That they don't think it was a freak show. That they don't think it was one-dimensional, and beyond that, maybe we all should be thinking of demagogues. Because there's always been demagogues, and there always will be.

Like the Manson Family, Jones's cult remains seared into the national memory. Is that just a product of it coming in the 70s, at a time of great social change, like the Manson attacks a decade earlier?

Jonestown, in its way, ranks with the Kennedy assassination, it ranks with 9/11—it's an event whose horror is so vast that it's hard to conceive it actually happened. And from that event, one phrase about it entered the national lexicon, "Don't drink the Kool-Aid." Which is supposed to mean, "Don't fall for crazy leaders that make you do insane things." But it wasn't even Kool-Aid! A lot of the victims were held down and forcibly injected with it, which is murder. And beyond that, they weren't idiots falling for some kind of fraud. If we can try to understand what happened to people here in a wider sense, it's going to make us look harder at how we tend to buy in to demagogues. If we are going to stop falling for them, then maybe we need to understand the process a little better.

When Leo Ryan, the congressman, came [to Guyana] and brought the media, it happened to be the tipping point. Jones was looking for some final big dramatic act that would make his name live on in history. If it hadn't been Leo Ryan, I believe it would have been something else. Ryan happened to be the trigger, but that trigger was going to be pulled soon, one way or another. When we look back, we can loathe Jim Jones, we can hate what he did, but he accomplished, in a personal sense, what he wanted. He wanted to be famous. He wanted to be remembered. And he is.

This interview has been edited and condensed for clarity. Learn more about Guinn's new book, which drops Tuesday, here.