(CNN) Sen. Chris Coons, a Democrat on the Senate's Foreign Relations Committee, had just finished his train commute from Delaware to Washington on Tuesday morning when he learned the news.

Secretary of State Rex Tillerson had been fired.

"I turned to (my staffer) and I said, 'Please just tell me it's going to be a calm day, nothing much going on. I've got a very full plate. I just need an ordinary day,' " Coons recounted.

The staffer looked at Coons and asked if the senator was cracking a joke. Then he told Coons, "The President just fired the secretary of state in a tweet."

Even in Washington, which has become acclimated to a rigorous pace of news dominated with presidential tweets, staff shake-ups and quickly evolving storylines, President Donald Trump's announcing his decision Tuesday took members of Congress (as it did Tillerson) by surprise. Across Capitol Hill, aides and members were scrambling to figure out what had just happened, with many learning the news from reporters clamoring the halls for answers. Members -- even those on relevant committees -- lamented they'd been given no warning that the firing was imminent.

"Well, I mean the way that this all happened obviously is a concern," said Sen. Jeff Flake, an Arizona Republican. "To find out you've been fired by tweet is not exactly reassuring in terms of the conduct of government."

The chairman of the Senate's Foreign Relations Committee, Republican Sen. Bob Corker of Tennessee, learned Tillerson was leaving from news reports and didn't get a call from Trump until 9:58 a.m. ET, more than an hour after the news had broken.

"I heard about it like so many things," Corker said, looking at a group of reporters peppering him with questions. "I heard about it from y'all."

Compounding the feeling of volatility on the Hill was the fact that just hours after Tillerson was let go, Undersecretary for Public Diplomacy Steve Goldstein, a top aide, was also fired.

Tillerson's firing had a real and immediate impact on the GOP's agenda in Congress. The Senate -- already swamped with a banking bill, sex trafficking legislation and an upcoming federal spending deal -- learned Tuesday that it would now have to devote significant floor time not only to confirming Tillerson's replacement, who Trump named as CIA Director Mike Pompeo, but also to confirming a new CIA director to replace Pompeo.

"With everything else we have to do around here, having the prospect of two additional confirmation fights perhaps is going to be a challenge," Sen. John Cornyn of Texas, the majority whip and second ranking Republican in the chamber, told reporters.

But while the timing of Tillerson's ouster caught Capitol Hill off guard, the fact it happened did not.

"I don't think this shocked a lot of people," Sen. Richard Shelby, a Republican from Alabama, told CNN. "This has been going on since before around Thanksgiving. I think people thought ... not if, but when."

Still, lawmakers said, the firing had come at a pivotal time for US foreign policy, just as Trump had announced last week that he would meet with North Korea's leader and as the President had just announced new tariffs on imported aluminum and steel. If members had once seen Tillerson as a steadying force in the White House, that channel had just evaporated. And it came just a week after Gary Cohn, whom members described as another voice of reason in the administration, had quit his post as a top economic adviser.

"The last thing we need at this time in the world is the chaos the administration has created," said Sen. Bob Menendez of New Jersey, the top Democrat on the Foreign Relations Committee.

"He's running our country more like a reality TV show than the most influential and powerful country on Earth," said Coons.

For months, Tillerson and Trump have not seen eye to eye, a fact several members of Congress have been privy to. After news broke that Tillerson had called Trump "a moron" last year, the President's frustration with his secretary of state never ceased to hinder their relationship. Trump and Tillerson disagreed on a whole host of foreign policy issues, from Iran to North Korea to the Paris climate deal. Adding to the tension was a simple distinction in how both men approached their jobs. Corker described Trump as "entrepreneurial" in his approach to foreign policy, while Tillerson -- who came from a job as CEO at Exxon Mobil -- had tended to be more "process oriented."

"There were just differences in style," Corker remarked. "I don't share conversations, but I have a close enough relationship with both of them to understand very well the relationship."

"It was not a long-term tenable situation to have ongoing tension and conflicts between the President and secretary of state," Sen. Ted Cruz, a Texas Republican, told CNN.

Members acknowledged Tuesday that Tillerson may not be the last Cabinet member shake-up. Trump said Tuesday that he was "close" to having the Cabinet he wanted, an allusion that more news could be coming.

Sen. John Kennedy, a Louisiana Republican, said the GOP had discussed Tillerson's firing at lunch and added that "the vice president thanked Secretary Tillerson for his service to America. We all joined in that."

"Every president has his own management style, including President Trump. It's not a criticism, it's just a fact. As we say in Louisiana, President Trump is a hard dog to keep on the porch. He's not a porch dog, he's a running dog, and likes to do things his way," Kennedy said.

Responding to the President's statement that he almost has the Cabinet he wants, Kennedy smiled, and said, "That means he's got a little more running to do, maybe."