Republican presidential nominee Donald Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE took to Twitter Sunday night to again attack rival Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE over her use of a private email server while she was Secretary of state.

“Lyin’ Hillary told the FBI that she did not know the ‘C’ markings on documents stood for CLASSIFIED. How can this be happening?” he tweeted.

Lyin' Hillary Clinton told the FBI that she did not know the "C" markings on documents stood for CLASSIFIED. How can this be happening? — Donald J. Trump (@realDonaldTrump) September 4, 2016

However, several people on social media noted that FBI Director James Comey has said the "C" stands for confidential.

It stands for "confidential." https://t.co/FgkElsSoOP — Chris Cillizza (@TheFix) September 5, 2016

"C" marking actually means "confidential". Not "CLASSIFIED". https://t.co/Q7guN5YY1s — Steve Kopack (@SteveKopack) September 5, 2016

(C) stands for CONFIDENTIAL. Confidential, Secret, Top Secret are levels of classification. DoD Directive 5200.01. https://t.co/j3jzMrIg5z — John Noonan (@noonanjo) September 5, 2016

Trump campaign manager Kellyanne Conway also piled on Sunday night.

A former U.S. senator, former first lady & certainly the sitting Sec of State should know what the "c" in classified material means. — Kellyanne Conway (@KellyannePolls) September 5, 2016

Trump also commented on Clinton's schedule for Labor Day, which include several stops at parades and events to mark the holiday that celebrates the labor movement.

“The polls are close so Crooked Hillary is getting out of bed and will campaign tomorrow,” he wrote.

The polls are close so Crooked Hillary is getting out of bed and will campaign tomorrow.Why did she hammer 13 devices and acid-wash e-mails? — Donald J. Trump (@realDonaldTrump) September 4, 2016

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The FBI on Friday released a detailed report on its investigation into Clinton’s use of a private email server, including the summary of its three-hour interview with the former secretary of State.

But Sen. Tim Kaine Timothy (Tim) Michael KaineTrump meets with potential Supreme Court pick Amy Coney Barrett at White House Names to watch as Trump picks Ginsburg replacement on Supreme Court Barrett seen as a front-runner for Trump Supreme Court pick MORE (D-Va.) on Sunday defended his running mate.

"The reason these materials are being made public is that Hillary Clinton said, 'I want the public to see them,' " Kaine said on ABC's "This Week."

"It demonstrates in very significant detail why the FBI chose not to go forward with any additional proceeding."