Mueller transformed the nation's premier law enforcement agency into a terrorism-fighting force after the September 11 attacks and later was special counsel in the Justice Department's investigation into whether the Trump campaign illegally coordinated with Russia to sway the 2016 presidential race. He died at 81.

The lawyer served as special counsel overseeing the investigation into Russian interference in the 2016 election.

Family says Mueller, who also examined Russian interference in 2016 election that Trump won, ‘passed away last night’