1) could happen. When I lived in Boston and was not into Chinese food, I went to the Chinatown to buy something per my friend’s request. So I would walk into one store, show them the package with the letters, get sent somewhere else, and finally in store nr5 I was sold that product. The stores were very small. Of course now I won’t remember where the heck it was, but for sure, if in 6 months people were poisoned by my purchase, for sure, for sure, I’d walk through all the stores of Chinatown, dragging the police with me, to find the one. You can imagine how it would look to me - I unbeknownst bought a poison from a store. It is a public danger! I would never say, I don’t remember, I’d crawl through all of them, and btw, hire a Chinese translator. (Another key - only one was selling what I was looking for in my case, so it was easy).
2) it is a very different story. It is not one person dying. It is something divided between four people so all of them die. I have read about the situations when very fast-acting poisons, presumably cyanides, were injected to mimic death from a heart attack. But again, into one person, not four.
I am not sure everyone imagines how people feel and behave when someone has been poisoned in their house, and they know they are innocent. Most of all, they are scared that the poison is still in the house and afraid to enter it.
