Sen. Angus King, I-Maine, says that former FBI deputy director Andrew McCabe's firing late Friday appears to be an act of revenge by President Trump.

"The whole thing appears -- at least at this point, we're going to find out more in the coming weeks -- but it appears to have been compressed in order to take vengeance on this guy for some reason," said King on Sunday. "I don't think that's the way we should be governing. So we have to find out the facts of what he did and if he did then some punishment was necessary."

Attorney General Jeff Sessions fired McCabe on the recommendation of FBI officials following an internal inspector general's (IG) report into the FBI's actions in the run-up to the 2016 election. McCabe has called his dismissal a part of what he said was a "war" on the FBI.

King said the issue of McCabe's termination, which took place just two days before what would be his retirement after 21 years at the bureau, is a major issue in his departure. He called the "rush" to terminate McCabe just before he became eligible to receive his pension struck him as "mean-spirited."

"It was clearly rushed and I think there are questions about that and whether the administration was putting pressure on the Justice Department to take this action," King said.

A report by the IG found evidence that McCabe had questionable contacts with a reporter and was not fully forthcoming when asked about it about an investigation concerning the Clinton Foundation. Those familiar with McCabe's side of the story say he was authorized to talk to reporters.

"We've got to see that inspector general's report. I don't want to go on press reports of pieces of it. A long time ago, I learned there are two sides to every story and I want to see what the inspector general says. I want to see what Andrew McCabe has in the way of a response," said King.

King also said that it would be a "huge mistake" for Mr. Trump to fire special counsel Robert Mueller, whom he described as being "as straight an arrow as there is in America."

"He's just doing his job. And for the administration to keep trying to undercut what they're trying to do -- the president keeps saying there's no story here, they didn't do anything wrong. If they didn't do anything wrong, why are they going to such extreme lengths to undermine this investigation, which is being carried out in a very responsible way?" King questioned.

If Mr. Trump attempts to terminate Mueller prematurely from the investigation, King said, "it will be a true constitutional crisis."