(FILES) L-R: US President Barack Obama (L), Attorney General Eric Holder, Secretary of Homeland Security Janet Napolitano and Director of the Federal Bureau Investigation (FBI) Robert Mueller stand during the National Anthem at the National Peace Officers Memorial Service, an annual ceremony honoring law enforcement who were killed in the line of duty in the previous year, at the US Capitol in Washington, DC, May 15, 2013. Mueller, the former FBI director who led a politically explosive investigation into President Donald Trump, has died aged 81, US media reported Saturday. (Photo by Saul LOEB / AFP via Getty Images)