Written by Tim Starks

The Department of Justice said Thursday that it seized approximately $1 billion worth of bitcoin, its biggest cryptocurrency seizure ever.

The announcement solves a a years-old mystery about the shuttered Silk Road dark web market for illegal drugs and other unlawful goods, widely regarded as the largest and most extensive dark web marketplace of its time before its 2013 demise.

The law enforcement action  solves another riddle about a bitcoin wallet that just saw a nearly identically valued amount of cryptocurrency withdrawn after sitting dormant for a long time.

“The successful prosecution of Silk Road’s founder in 2015 left open a billion-dollar question. Where did the money go?” said U.S. Attorney David Anderson. “Today’s forfeiture complaint answers this open question at least in part. $1 billion of these criminal proceeds are now in the United States’ possession.”

Motherboard reported Wednesday on the Election Day emptying of the wallet. Then the complaint, filed Thursday, detailed how federal investigators tracked down someone identified only as “Individual X,” who had hacked the funds from Silk Road — much to the dismay of Silk Road creator Ross Ulbricht.

“According to the investigation, Ulbricht became aware of Individual X’s online identity and threatened Individual X for return of the cryptocurrency to Ulbritcht,” the complaint reads. “Individual X did not return the cryptocurrency, but kept it and did not spend it.”

On Tuesday, “Individual X” signed an agreement to forfeit those Bitcoins, whereupon feds took over the money.

The U.S. government still must prove its case in court to retain the cryptocurrency.