As for how he was fired, a letter was sent to FBI headquarters hours before the announcement was made but no one at the FBI had bothered to tell Comey about it.
As for how he was fired- Trump didn't have the balls to do it in person- or even call him and tell him he was being fired.
He sent his bodyguard with a sealed letter to the FBI headquarters- when Comey was 3,000 miles away.
The news was leaked to the press before the letter was delivered.
https://www.nytimes.com/2017/05/09/...-live.html?smid=tw-nytpolitics&smtyp=cur&_r=1
No Balls Trump.