Democratic Sen. Claire McCaskill (MO) said deputy Attorney General Rod Rosenstein told the full Senate in a classified briefing that he knew President Donald Trump was going to fire FBI Director James Comey prior to authoring his memo recommending Trump fire Comey.

Rosenstein’s controversial memo criticized Comey for his management of the investigation into how Hillary Clinton’s handled her email as secretary of state. Attorney General Jeff Sessions then cited Rosenstein’s memo in a letter to Trump that recommended he fire Comey. Trump provided both documents with his letter informing Comey of his termination.

The White House initially suggested Rosenstein’s recommendation explained Comey’s firing, but Trump later said in an interview with NBC News that he decided to fire Comey from the Justice Department “regardless of the recommendation.”

McCaskill, a former prosecutor, said she reserved judgment about the briefing because members of Congress still haven’t seen all the facts, relevant documents and heard sworn testimony. She added that Rosenstein “was very careful about not going into any details surrounding the removal of Comey because he wants to give Robert Mueller the opportunity to make an independent decision” about how to proceed.

Sen. Dick Durbin (D-IL) said Rosenstein told them he was not pressured into writing the memo. But Durbin was left with many question unanswered. “There are a lot of missing pieces,” Mr. Durbin said. He identified specifics regarding what Mr. Trump had said on May 8, and what role Attorney General Jeff Sessions played in the decision to fire Comey.

Sen. Lindsey Graham (R-S.C.), chairman of the Senate Judiciary subcommittee on crime and terrorism, said, “the takeaway I have is that everything he said was that you need to treat this investigation as if it will be a criminal investigation.” Graham added, “I think the biggest legal challenge seems to be that Mr. Mueller’s going to proceed forth with the idea of a criminal investigation not a counterintelligence investigation.”

The New York Times suggests that, “The disclosure by the senators raises the possibility that Mr. Rosenstein could become a witness in the investigation being run by the special counsel, Robert S. Mueller.”