If you thought your or your kid's roommate problems were bad...

Parent Cafe
3

And another case:

https://www.google.com/amp/s/articles.nj.com/news/index.ssf/2011/02/thallium_is_favored_method_of.amp

Apparently the original thallium poisoning case was pretty well known in China and supposedly thallium is a common ingredient in rat poison sold in China.