The president took notice of comments made by Connecticut Sen. Richard Blumenthal on Wednesday morning.
But Blumenthal said the president's comments wouldn't silence him.
Blumenthal, a Democrat on the Judiciary Committee, compared the recent firing of FBI director James Comey to that of Watergate.
He also called for an independent prosecutor to investigate it.
"It certainly is Nixonian in its tone to fire someone of this stature in the midst of an investigation is absolutely unfathomable for the commander-in-chief of the United States to do in the midst of an investigation," Blumenthal said.
The firing by the White House came after the FBI sent a letter to Congress admitting Comey's claims about Hillary Clinton's aide's emails were misleading.
The dismissal also came as Comey and the FBI were investigating potential Trump campaign contacts with Russia during the presidential campaign.
President Donald Trump posted about the firing on Twitter.
"Comey lost the confidence of almost everyone in Washington, Republican and Democrat alike," he said. "When things calm down, they will be thanking me!"
Blumenthal questioned the decision during an interview with CNN.
"What we have now is really a looming constitutional crisis that is deadly serious," he said.
Trump fired back in a series of Twitter rants.
"Watching Senator Richard Blumenthal speak of Comey is a joke," he wrote. "'Richie' devised one of the greatest military frauds in U.S. history."
Watching Senator Richard Blumenthal speak of Comey is a joke. "Richie" devised one of the greatest military frauds in U.S. history. For....— Donald J. Trump (@realDonaldTrump) May 10, 2017
"For years, as a [politician] in Connecticut, Blumenthal would talk of us great bravery and conquests in Vietnam - except he was never there," Trump said.
years, as a pol in Connecticut, Blumenthal would talk of his great bravery and conquests in Vietnam - except he was never there. When....— Donald J. Trump (@realDonaldTrump) May 10, 2017
"When caught, he cried like a baby and begged for forgiveness and now he is judge and jury," he continued. "He should be the one who is investigated for his acts."
caught, he cried like a baby and begged for forgiveness...and now he is judge & jury. He should be the one who is investigated for his acts.— Donald J. Trump (@realDonaldTrump) May 10, 2017
Later in the morning, Blumenthal posted his own Tweet in response to Trump's onslaught.
"President Trump, your bullying won't silence my calls for an independent prosecutor and investigation," he said.
President Trump - Your bullying won’t silence my calls for an independent prosecutor and investigation.— Richard Blumenthal (@SenBlumenthal) May 10, 2017
Trump said he was working to restore trust and confidence in the FBI.
His administration said Comey's handling of the Clinton email investigation justified his dismissal.
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