The FBI's Russia investigation, which was ultimately taken over by special counsel Robert Mueller, began in July 2016 after the FBI learned that a former Trump campaign aide, George Papadopoulos, had been saying before it was publicly known that Russia had dirt on Democratic opponent Clinton in the form of stolen emails. Those emails, which were hacked from Democratic email accounts by Russian intelligence, were released by WikiLeaks before the election in what U.S. officials have said was an effort to harm Clinton's campaign and help Trump.