German authorities arrested the suspected administrator of a darknet platform that sold illegal weapons and drugs, federal prosecutors announced on Monday. The site, which had some 20,000 members, is reportedly responsible for selling weapons to the teenager who killed 10 people including himself at a shooting in Munich last year.

The 30-year-old, whose name was not released, was arrested on Thursday after a months-long investigation into his business. Police suspect that he has run the darknet site since 2013, trafficking not only in drugs and weapons but also in credit card numbers and account passwords.

Police seemed fairly confident that they had apprehended the right man, pointing to information on a server they confiscated during his arrest, as well as drugs he had stored in small quantities in his apartment.

The July 22, 2016 shooting in Munich shocked Germany, a place where such occurrences are rare for a country that allows (under certain restricted circumstances) private gun ownership. The 18-year-old perpetrator killed 9 people and injured 36 more after he opened fire at a McDonald's franchise near a shopping mall.

He killed himself before he could be apprehended by police, leaving his motive shrouded in mystery, though prosecutors have said he displayed an intense interest in other mass shooters such as Norwegian right-wing terrorist Anders Bering Breivik and Columbine High School killers Dylan Klebold and Eric Harris.