What would you do if a significant amount of money had been stolen from a loved one ?

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The subject says it all...what would you do if you knew the name of the person (as well as a few of their social media accounts and their approximate whereabouts) who had stolen a significant amount of money from a vulnerable person you love and the legal system has let them down ? The money isn't as important now as the loved one took their life, but the pig who stole it still has it and is quite wealthy anyway (likely from grifting others) but is very careless and from my initial reconnaissance, not particularly tech savvy. It's time for some 'theoretical/ fantasy only of course, wink wink, nudge nudge, karmic retribution.

So...what would you do ?