The Instituto Goiano de Radioterapia had moved to new premises years earlier, leaving behind a teletherapy machine in a building whose ownership was being disputed in court. The clinic's owners had written to the National Nuclear Energy Commission warning that a radioactive source was being left in an insecure site. A court order prevented them from removing it themselves. On September 11, 1986, the Court of Goias formally noted that it knew about the material. Nothing was done. By May 1987 looters had stripped the building of gates, windows, roof. When Roberto and Wagner broke in to salvage metal on September 13, 1987, the device was still there, sitting in what had been a treatment room, its shielding lead and steel. They did not know what it was. They carried it home in a wheelbarrow. The removal took hours, and by the time they got it to Roberto's backyard, both men had already received dangerous doses of radiation.

Roberto's family, his neighbors, and eventually a neighborhood scrap dealer named Devair Ferreira all saw the glow. It was the Cherenkov-like emission from the caesium-137 salt itself, a feature of high-activity radiation sources exposed to the open air. Devair bought the cylinder from Roberto and displayed it to friends. He gave small amounts of the powder to relatives as a kind of novelty - something magical to take home. His brother Ivo carried some back to his own house, where his six-year-old daughter Leide das Neves Ferreira saw the glowing dust, rubbed it on her skin, and, while eating an egg sandwich whose shell had become contaminated, absorbed an internal dose of about one gigabecquerel. She received a total dose of 6.0 grays, and nothing medicine could do would save her. Devair's wife, Maria Gabriela Ferreira, noticed that many of the people around her were becoming sick at the same time. On September 28, 1987, fifteen days after the original theft, she retrieved the material from a rival scrapyard where Devair had taken it and carried it herself, in a plastic bag, on a public bus to a hospital.

Four people died. Leide das Neves Ferreira was six years old. When international medical teams arrived to treat her, they found her alone in an isolation room because the hospital staff were afraid to enter. She lost her hair. Her body swelled. Her kidneys and lungs failed, and she died on October 23, 1987, at the Marcilio Dias Navy Hospital in Rio de Janeiro, of septicemia following radiation exposure. Her burial in Goiania was met with a riot of more than 2,000 people who feared her body would poison the earth. She was buried in a lead-lined fiberglass coffin despite stones thrown to block the cemetery road. Maria Gabriela Ferreira, 37, died the same day as her niece. Admilson Alves de Souza, 18, a scrapyard worker, died on October 28. Israel Batista dos Santos, 22, who had worked on the source primarily to extract its lead, died on October 27. Devair Ferreira survived a dose of 7 grays. He died in 1994 of cirrhosis, alcohol, and what was described as depression.

On the morning of September 29, 1987, a visiting medical physicist used a scintillation counter at the hospital and confirmed what nobody had yet quite believed: there was a radioactive disaster unfolding in Goiania. By the end of that day the city, state, and national governments all knew. Within days, 130,000 residents flooded local hospitals worried they had been exposed. Of the 112,000 examined, 249 were found contaminated. The cleanup was enormous. Topsoil was removed from dozens of sites. Forty-two houses were entered and searched; several were demolished. Fourteen cars, three buses, and even five pigs were contaminated. Fifty thousand rolls of toilet paper had been handled and had to be removed. Painted surfaces were scraped; floors were washed with acid and Prussian blue, the ferrocyanide pigment that binds caesium and carries it out of the body. Even after the cleanup, roughly 7 terabecquerels of radioactivity remained unaccounted for - meaning 7 trillion nuclear disintegrations per second, somewhere, still radiating. The original site of the clinic has since been replaced by the modernized Goiania Convention Center, a building whose everyday use hides what happened there.

The International Atomic Energy Agency called Goiania "one of the world's worst radiological incidents." On March 17, 2000, a federal court ordered the National Nuclear Energy Commission to pay R$1 million and guarantee medical and psychological treatment for the victims, their descendants down to the third generation, and the people of Abadia de Goias, where some of the waste was stored. The state created the Fundacao Leide das Neves Ferreira in February 1988 to study the contamination and help survivors. Survivors still report that everyday Brazilians treat them warily, as if radiation might be contagious. In 2007 the Oswaldo Cruz Foundation found that the rate of caesium-related diseases in accident survivors was no higher than the general population - cold comfort to people whose lives had been reshaped. A 1990 Brazilian film, Cesio 137, dramatized the story; Liliana Colanzi's 2022 collection You Glow In The Dark returned to it in fiction. What happened in Goiania is the kind of disaster that begins with a failure of paperwork and ends with a child in a lead coffin.