I am sad to inform you that you have no future as a supervillain.
With a radiation source like this even a dust sized particle, if ingested or inhaled, is enough to cause excruciating death. Anything that turns the capsule into a powder and releases it into the air near a large group of people or into a water source or even a public pool could cause mass fatalities.
Mass fatalities, no. Source: I have worked in Chernobyl.
But anyway that's a way better suggestion because you can split one source into a vast multitude of opportunities to slit into someone's pillow. So excruciating death it is.
iirc the comments from the previous articles on this topic, then yes. storing the capsule a few meters away for extended periods of time will cause leukemia - a lot faster than smoke will cause lung cancer.
Radiation-poison people? There's not enough material, even if it was Uranium or Plutonium to make any sort of bomb IIRC, you need kilos for that not, (micro)grams.
I think that's probably the biggest risk - you could just plant it somewhere where it wouldn't be found for a while, giving everyone around it major radiation sickness.
Wikipedia doesn't say that, but it was given as a rate at one meter away. If you were to hold it in your hand or put it in your pocket, you'd give yourself radiation burns pretty much instantly. Imagine sticking this under(or even inside, it doesn't matter with gamma) a politician's desk where they sit for a few hours a day - at the beginning they wouldn't feel much, but after just one day the burns they suffer would be enormous.
Imagine if some aboriginals found it and tried to make jewellery out of it. Probably not unlikely, seeing that it's a heavy metal object that can be drilled so that you can attach a necklace. The wearer would be in deep trouble.
