It is now assumed that this already happened, in 2011, in a Bulgarian umbrella attack in Germany's crime capital, Hanover.
My somewhat unfounded guess is that the perpetrator himself perished not too long after the victim, which would explain why the case is still unsolved.
It seems like it's easily detected though? Is there any legitimate reason in today's world for someone to have ~80x above mercury's human toxicity limit, besides those actually working with the stuff in the industry?
