There's no need to "fire" Mr. Sessions without going to him first and asking for his voluntary resignation.
If Jeff is reasonable (and I sense that he will be), he may step down with a full pension, etc. That's the best way out.
I have to admit I'm disappointed with him. He was an early supporter of Mr. Trump, and was saying the right things on immigration before the 2016 election.
Can't figure out why he went south on us.