Sen. John McCain (R-Ariz.) slammed President Trump Tuesday for firing FBI Director James Comey, telling a group of foreign officials and experts that his dismissal will not end the investigation into Russian interference in the 2016 election, according to a Washington Post report.

"I regret it, I think it's unfortunate," McCain said during a meeting with the Munich Security Conference. "The president does have that constitutional authority. But I can't help but think that this is not a good thing for America."

McCain said the FBI's investigation into whether Trump campaign aides colluded with Russian officials to sway the election will go on.

"This scandal is going to go on. I've seen it before," McCain continued. "This is a centipede. I guarantee you there will be more shoes to drop, I can just guarantee it. There's just too much information that we don't have that will be coming out."

If Trump intended to disrupt the FBI investigation, McCain said, it wouldn't work.

The Arizona senator called the president's decision to fire Comey "unprecedented."

McCain also recalled former President Richard Nixon's "Saturday Night Massacre" in 1973, when Nixon fired special prosecutor Archibald Cox as Cox investigated the Watergate break-in. Cox's firing preceded the resignation of Nixon's attorney general and deputy attorney general, who both refused to fire Cox at Nixon's behest.

McCain said the position as FBI director is "probably the most respected individual in all of the American government," adding that he is "very sorry that this has happened."

McCain issued a statement earlier Tuesday saying he is "disappointed" with Trump's decision, and calling for a special congressional committee to take the lead on the Russia probe.