The “lone hacker” who provided WikiLeaks with a trove of emails from the Democratic National Committee was an officer of Russia’s military intelligence directorate, GRU, and working out of their Moscow headquarters at the time of the massive hack.

The Daily Beast reported Thursday that special counsel Robert Mueller has taken over the investigation into the hacker, known as Guccifer 2.0, and has brought in FBI agents who discovered the hacker’s Russian identity.