By Trump, or Trump and Sessions working as a team.
You have to consider that the black hats are, at least at first, pretty good at hiding. I think Rosenstein is an unwilling white hat in this scheme. He had to write the fire Comey memo (FBI Director reports to DAG) if ordered/asked by Sessions. And as cover, it serves him well. Yeah, I'm with you guys, fire Comey - meanwhile Rosenstein's handling of Mueller is an unknown, other than there is a pretty good expectation Mueller is going to go hard against Trump, so that a clean bill from Mueller has street cred.
How can Mueller go hard against Trump when there was no collusion or other crime committed in the Russia collusion regard?