Two scavengers named Roberto dos Santos Alves and Wagner Mota Pereira saw their opportunity and swooped in to steal whatever they could carry. "Whatever they could carry," as you can guess, turned out to be the caesium-137 radiotherapy unit, which they brought back home and promptly tore open like a Christmas present.
They removed the core and smashed it open, finding a blue glowing substance inside that mystified them. This was the caesium, and predictably, it poisoned the everloving shit out of both men, eventually causing internal damage, contact burns and the need for amputation. Luckily, they were able to take the exposed core to a scrapyard before any of that happened.
"Hey look, that girl could look after it for a while. Pass her a 20. We're creating jobs here."
From the scrapyard, things only got worse. No one knew what the glowing substance was, outside of maybe Predator blood, so no one felt the need to handle it with anything resembling caution. The junkyard owner wanted to make a ring for his wife out of it, several people smeared it on their bodies like paint and a 6-year-old girl even wound up eating some of it, because that's what you do with a glowing blue mystery from a garbage dump.
Finally, after numerous people started getting frighteningly sick all at the same time, a local woman collected the substance and took it to a hospital to be examined, rightly suspecting that perhaps the fantastic powder of dreams was to blame. A visiting physicist detected the danger almost immediately.
"Alright, let's take a look at what we've got he -- SWEET JESUS."
All told, 250 people had been contaminated by the exposed material, four of whom received fatal doses and died. The people in charge of IGR were charged with criminal negligence for leaving the caesium unit essentially unguarded in a derelict building.