President Donald Trump fired FBI Director James Comey on Tuesday — and the startling move has many thinking back to a night in 1973.

The firing comes after months of Comey making his own headlines. He’s become infamous for briefly reopening an investigation of Hillary Clinton’s email server days before the U.S. voted for president, and more recently for testifying before the Senate Judiciary Committee and confirming that there's an investigation into whether Trump administration officials colluded with Russia ahead of that election.

Comey's removal amid an active investigation involving the White House recalls something President Nixon did before he resigned.

Many politicians, critics, and political commentators on Twitter are drawing parallels between President Trump’s act and President Nixon’s “Saturday Night Massacre.” The latter happened on October 20, 1973, during the Watergate scandal—a scandal involving Nixon campaign officials breaking into the offices of the Democratic National Committee. During the "Saturday Night Massacre," President Nixon ordered the firing of Archibald Cox, a prosecutor brought in to investigate the break-in and subsequent cover up. His firing led to the resignation of Attorney General Elliott Richardson and Deputy Attorney General William Ruckelshaus.

Senator Joe Manchin, a Democrat from West Virginia, likewise made the comparison, noting it  “didn’t come out so well” for Nixon.

Senator Bob Casey, a Democrat from Pennsylvania, demanded that the investigation of ties between the Trump team and Russia continue.

Senator Patrick Leahy, a Democrat from Vermont, called the firing of Comey "nothing less than Nixonian.”

Senate Minority Leader Chuck Schumer, meanwhile, said that if the Russia investigation is not continued it will suggest the White House has something to hide.

Senator Lindsey Graham, a Republican from South Carolina who is pressing for a closer look at Trump's Russian business ties, echoed the need to keep the investigation going.

President Nixon's official library also chimed in, with its Twitter account challenging the idea that Trump's behavior is "Nixonian."

Nixon's "massacre" was no less controversial, though. As The Washington Post reported at the time, White House aides were “visibly shocked by the developments.”

The event was also of note because it illustrated how Nixon was attempting to shutter the investigation into Watergate. The president resigned less than a year later on August 8, 1974.

This isn’t the first time critics have connected President Trump to the “Saturday Night Massacre,” either.

When President Trump fired acting-Attorney General Sally Yates in January, it prompted “Monday Night Massacre” to trend on Twitter — and just yesterday, Yates testified against the president. As Time pointed out, Yates’ firing was shocking but not as significant as Nixon's action.

The New York Times does note that the firing of Comey is the first time such an event has happened since Nixon's firing of Cox, and is unique in that regard. History, though, will be the best judge of whether this is the moment that led to President Trump’s undoing.