After President Donald Trump blasted James Comey as one of several “dirty cops” who dug into Russian meddling in the 2016 election, the former FBI director lashed out at the GOP, decrying “witness intimidation.”

“This is not okay, not normal,” Comey wrote Monday on Twitter in the hours after Trump’s statements to reporters. “That the witness intimidation continues while hundreds of thousands of honest public servants are without pay moves it from just outrageous to unconscionable. Can Republicans hear the past asking, ‘At long last, have you left no sense of decency?’”

This is not okay, not normal. That the witness intimidation continues while hundreds of thousands of honest public servants are without pay moves it from just outrageous to unconscionable. Can Republicans hear the past asking, “At long last, have you left no sense of decency?” — James Comey (@Comey) January 14, 2019

In his press briefing earlier that day before he left for a New Orleans event, Trump expressed frustration when asked to remark on the Russia investigation, declaring he never worked for the foreign country and adding: “I think it’s a disgrace that you even asked that question because it’s a whole big fat hoax. It’s just a hoax.”

Continuing to rage against special counsel Robert Mueller’s investigation, the president labeled Comey, former acting FBI Director Andrew McCabe and former FBI agent Peter Strzok as “known scoundrels.”

Trump also attempted to undermine the legitimacy of the Russia inquiry by claiming it was started because he fired Comey.

He then took a moment to single out Comey.

“I have done a great service for our country when I fired James Comey because he was a bad cop and he was a dirty cop and he lied,” Trump said. “He really lied.”

The last line of Comey’s seemingly retaliatory tweet appears to refer to the infamous 1954 Army-McCarthy hearings, which were launched after then-Sen. Joseph McCarthy (R-Wis.) alleged that the U.S. Army had flimsy security at one of its top-secret facilities.

But the move backfired when the Army said McCarthy had asked for special treatment of a subcommittee aide who’d just been drafted.

In a heated courtroom battle, McCarthy accused a young lawyer who worked at the same firm as Joseph Welch, the Army’s counsel, of having Communist ties.

With a withering response, Welch replied: “Let us not assassinate this lad further, senator. You have done enough. Have you no sense of decency, sir? At long last, have you left no sense of decency?”

Last week, a New York Times report revealed that following Comey’s ouster, the FBI allegedly looked into whether Trump was serving as a Russian agent as well as whether he had obstructed justice in firing the intelligence official.

In an interview Saturday with Fox News’ Jeanine Pirro, Trump called it “the most insulting article I’ve ever had written,” claiming that “if you read the article you’ll see that they found absolutely nothing.”