Goiana was Cesium-137.
There have been several incidents with Cobalt-60 sources, including one in 2010 in Dehli, India, and another in 2000, in Thailand. And in some cases, the radioactive material has ended up being recycled into new products; for example - incidents which actually happened: water-dishes for pets, and belt-buckles sold from discount websites. In these cases, the radioactivity was detected by random spot-checks. There are probably products out there that have incorporated recycled radioactive substances, which made it through spot-checks and are sitting in people's homes, making them sick - and there is no way for us to know.
With regard to the cobalt 60 source: Wikipedia says it was 111 Tbq.
"Example: a 60Co source with an activity of 2.8 GBq, which is equivalent to 60 g of pure 60Co, generates a dose of 1 mSv at one meter distance within one hour."
A 1 Sv dose in 1 hour, is lethal.
Extrapolating 111 TBq to 2.8 GBq; (111,000/2.8 = 39,642
If they took it out of it's casing, they'd receive a lethal dose of radiation in less than 2 minutes. (depending on how close they stayed, and how long they stayed near it). Staying at least 400 cm away, would mitigate much of the beta particles, but not the gamma rays. Gamma rays are attenuated by the inverse square law, like any radiant energy. So distance is also your friend, but better still, an inch or so of lead.
They would not start feeling symptoms, until an hour or two later. Dizzyness, headache, nausea, vomiting. Later - worse symptoms appear. It will probably take a few days for them to die, and they may seek medical treatment, which may save them, depending on how long they were in close proximity to the unshielded source.