In 1985, the classic horror-comedy film Return of the Living Dead was unleashed upon the world. In it, a worker at a medical supply warehouse accidentally releases a chemical weapon while hazing a teenage employee. The weapon, now affectionately known as “Tar-man,” was a zombie sealed away in a rusty iron barrel that had been forgotten in the basement of the warehouse.

The Tar Man’s origins are explained in the film:

Frank: Lemme ask a question. You ever seen that movie, “Night of the Living Dead?”

Freddy: The one about the corpses eating people? Sure. That was one of the finest movies ever made. What about it?

Frank: Did you know it was based on a true case?

Freddy: Naw. Go on. You’re shitting me.

Frank: I’m dead serious.

Freddy: That’s not possible. They showed the zombies taking over the whole world. I would have heard about that.

Frank: Well, they changed the details for the movie. What really happened was that back about 1966, there was a chemical spill near Pittsburgh. It leaked down into the veteran’s cemetery and made some dead bodies act like they was alive.

Freddy: (Skeptical) What chemical?

Frank: It’s called 2, 4, 5, Trioxin and they were going to use it on marijuana or something. It was something Darrow Chemical was developing for the Army. They shut it down after the business with the corpses. And they told the guy that made the movie, that if he told the true facts, they’d sue his ass off. So he changed it all around.

Freddy: So what really happened?

Frank: Well, they shut it all down, and the Army took away the contaminated dirt and bodies, and they managed to keep it all a secret.

Freddy: So how come you know about it?

Frank: The Army transport department got their orders crossed, and they brought the bodies here instead to Darrow Chemical. Typical Army fuck-up, they put them here and forgot about them…

Despite its campy critique of the U.S. military, Return of the Living Dead’s plot is not entirely removed from reality. In truth, the U.S. military has purposely exposed American and Canadian civilians to dangerous chemical agents.

In the early 1950s, the U.S. Army Chemical Corps prepared a series of biological weapons tests in multiple cities across the United States and Canada. These experiments were executed in the mid-1950s through the late 1960s—not before a law was passed to shield private military contractors from all liability for public injury.

As Professor Lisa Martino-Taylor writes, this, in effect: “created a sanction-free military human test zone across North America and blocked legal recourse for victims.”

In short, the Army was ostensibly concerned that the Russians would expose American and Canadian civilians to dangerous agents, so the Army did it themselves in the name of mitigation.

As a part of the tests, the U.S. Army Chemical Corps released zinc cadmium sulfide “from airplanes, rooftops, and moving vehicles in 33 locations, mostly cities and towns, in the United States and Canada.” These cities included St. Louis, MO, Minneapolis, MN, Corpus Christi, TX, Fort Wayne, IN, Biltmore Beach, FL, and Winnipeg, MB. The cities were chosen because of their similarity to cities in the USSR.

In St. Louis, the Army’s dispersion methods were insidious. “The Army used motorized blowers atop a low-income housing high-rise, at schools and from the backs of station wagons” to disperse the chemical agent. Local officials were told that the “government was testing a smoke screen that could shield St. Louis from aerial observation in case the Russians attacked.”

Zinc cadmium sulfide itself is a fine powder “that is formed by heating zinc sulfide and cadmium sulfide together under very high temperature so that they fuse…Zinc cadmium sulfide is not a biologic weapon; it was a tracer used by the Army to imitate or simulate the dispersion of biologic weapons.” At the time, the compound was not believed to be dangerous to humans.

In the 1990s, as the Manhattan Project’s dark history of human radiation experimentation came to light (a story in of itself), then-President Bill Clinton established a congressional inquest to investigate it. As a result, many other instances of government-sponsored human experimentation came to light, including the zinc cadmium sulfide dispersal experiments. Victims soon came forward demanding answers.

At the behest of Congress, the National Research Council Committee on Toxicology began an official investigation of the dispersal experiments. In 1997, it published its findings as to the likelihood of public injury.

The Committee concluded:

“[G]iven the very small amounts of zinc cadmium sulfide to which people were exposed and the short duration of exposure, it is extremely unlikely that anyone in the test areas developed adverse health effects, such as lung cancer or infertility problems, from the Army’s releases of zinc cadmium sulfide.”

The Committee did not assess the ethical issues surrounding the Army’s decision to expose hundreds of thousands, perhaps millions, of Americans and Canadians to toxic compounds without their knowledge or consent. Neither did the Committee address the true concerns of survivors, that the zinc cadmium sulfide was irradiated by the Army Chemical Corps before dispersion.

Some may find the investigation to be a classic example of: “we investigated ourselves and found no harm.”

Over a decade later, in 2015, a Federal District Court in Missouri dismissed a class-action lawsuit made by Missourians who alleged harm from the zinc cadmium sulfide experiments.

Although the suit was dismissed because of U.S. sovereign immunity (the Federal Government can only be sued if it consents to be sued), the court relied on the National Research Council Committee’s report to support the fact that the plaintiffs’ injuries were unrelated to the dispersal experiment.

At the end of Return of the Living Dead, the zombie outbreak spreads from the medical supply warehouse to the neighboring cemetery. Eventually the outbreak hemorrhages to the surrounding town of Louisville, Kentucky. The U.S. Army is quickly notified and summarily nukes the entire town.

The film itself is purposefully campy and outlandish. For instance, it was the first zombie film to popularize the notion that zombies are motivated by a desire to eat brains. The film is now a cult-classic.

Given the real-life absurdities of a government willing to experiment on its own citizens without knowledge or consent, perhaps Return of the Living Dead ironically approximates something close to the truth.

That is what makes the film truly terrifying.