There are no details about how exactly police found the main actors, probably he was too easy going with his personal data.
Shiny-Flakes had a clearweb address (shiny-flakes.to), which was hosted in Tonga - and now links to a police recruitment campaign.
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There are no english reports on this yet. This is my summary based on the following newspaper report. Here's the english translation:
https://translate.google.com/translate?sl=de&tl=en&js=y&prev=_t&hl=de&ie=UTF-8&u=http%3A%2F%2Fwww.l-iz.de%2Fleben%2Ffaelle-unfaelle%2F2015%2F03%2Fleipziger-ermittler-nehmen-drogenversand-shiny-flakes-hoch-78227&edit-text=&act=url