One September morning in 1976, a bomb blew up a car as it was driving up Embassy Row in Washington, D.C. When police arrived at the scene, they found a human foot in the road, and a man lying on the pavement who was missing half his legs. Minutes later, he was dead.

That man was 44-year-old Orlando Letelier, the most prominent Chilean exile living in the U.S. The former ambassador had fled his country two years before to escape persecution under General Augusto Pinochet. Chile was an American ally during the Cold War, and it seemed unthinkable that Pinochet would be so bold as to carry assassinate him in the U.S. capital. But as we now know from declassified documents, that’s exactly what he did. In fact, he even considered killing his head of intelligence to cover his tracks.

Letelier had been an ambassador to the U.S. under Chile’s democratically elected president Salvador Allende, whose administration the CIA covertly undermined. On September 11, 1973, Pinochet succeeded Allende in a coup d'état. That same day, Pinochet’s people arrested Letelier and other officials from Allende’s government and sent them to concentration camps.

After nearly a year in prison, Chile released Letelier under international pressure from Secretary of State Henry Kissinger, among others. Letelier sought refuge the U.S., and while traveling through Venezuela to get there, he told The New York Times: “they're going to kill me.” The “they,” he seemed to imply, were the National Intelligence Directorate, or DINA—Pinochet’s secret police.

For two years, Letelier worked at the Institute for Policy Studies in D.C. His assistant Juan Gabriel Valdés—who now holds Letelier’s position of Chilean ambassador to the U.S.—said that during that time Letelier received threats slipped under his door.

“Orlando always dismissed our concerns, saying: ‘They would never dare to attack me in Washington,’” Valdés tells The Washington Post. “‘If they want to attack me, they will wait for me to be in Europe, particularly in [the Netherlands],’ where he traveled a lot.”

The day before Letelier’s assassination on September 21, 1976, he told a man who worked for him, Michael Moffitt, that he suspected DINA was behind recent attacks on Chilean exiles in other countries. Furthermore, he believed the secret police were spying on him. Moffitt and his wife, Ronni, were both in the car with Letelier when the bomb went off. He survived, but his wife did not. Amidst the carnage that day, Moffitt screamed about whom he thought was behind the attack: “Assassins, fascists!”

This wasn’t the first time that Chile tried to assassinate someone on another nation’s soil. In 1974, the country orchestrated a bombing that killed General Carlos Prats Gonzalez in Buenos Aires. The next year, agents opened fire on Bernardo Leighton, the vice president of Chile's Christian Democratic Party in Exile, and his wife while they were in Rome. Yet Letelier’s death was the first known act of violence against a Chilean exile in the U.S.

In addition, it was the FBI’s first case of state-sponsored international terrorism in D.C. Because of this, the bureau didn’t really know how to handle it.

“It was the first time we were dealing with a foreign government as a suspect,” says Carter Cornick, the FBI agent assigned to the Letelier case, according to The Washington Post. “The real issue to me was the potential for creating a precedent of assassinating foreign diplomats in the U.S., let alone in the heart of Washington. Every government has an obligation to protect its visiting diplomats.”

Over the next few years, the FBI uncovered the lower-level operatives who’d carried out the assassination. The main organizer was Michael Townley, an American who was working with DINA. Townley confessed that he’d recruited Cuban exiles living in the U.S. to place the bomb on the car.

Many speculated that the person pulling the strings at the highest level—the person who’d ordered the assassination—was Pinochet himself. However, the public didn’t learn this for sure until 2015, when President Barack Obama’s administration declassified intelligence documents about the assassination and delivered them to Chilean President Michelle Bachelet.

The documents show that Pinochet ordered the assassination directly, and that the U.S. knew this as early as 1978. Even so, the U.S. doesn’t seem to have used this information to challenge or reprimand him. Valdés speculates that the larger federal government’s desire to maintain a Cold War ally prevented the FBI and the Justice Department from seeking international justice. Pinochet died in 2006 without ever standing trial for the assassination, or any other human rights abuses he oversaw as Chile’s leader.