Link: http://www.latimes.com/politics/washington/la-na-essential-washington-updates-last-fbi-director-to-get-fired-before-1494368709-htmlstory.html
In 1993, President Clinton ousted William Sessions as FBI director after Sessions refused to voluntarily step down amid ethical concerns. It was the only time to happen in U.S. history, until Donald Trump fired James Comey.