Umm-what about this?
"But only one of those directors was ever fired by a president — William S. Sessions who had been appointed by President Ronald Reagan in 1987, but who was beset by allegations of ethics violations, such as disguising private vacations as law enforcement business, and using a chauffeured government limousine for personal transportation.
Because firing an FBI director is certain to bring accusations of playing politics with law enforcement against any president who chooses to do so, Clinton repeatedly asked Sessions to resign his post. But Sessions refused to step down.
So in July of 1993, saying that he had been advised by then-attorney general Janet Reno that Sessions “can no longer effectively lead the bureau and law enforcement community,” Clinton fired the FBI director — eventually appointing Freeh in his place"
Found here:http://heavy.com/news/2016/10/james-comey-fired-fbi-director-hillary-clinton-email-private-server-influence-election/
Looks like they found precedent and plagarized it...