WASHINGTON (AP) — A former Trump administration official who penned a scathing anti-Trump op-ed and book under the pen name “Anonymous” revealed himself Wednesday as a former chief of staff at the Department of Homeland Security.

The official, Miles Taylor, came forward six days before Election Day to criticize President Donald Trump as “a man without character.” He said he hoped other former administration officials will “find their conscience when they wake up tomorrow” and speak up, too.

Taylor has been an outspoken critic of Trump’s in recent months and had repeatedly denied he was the author of the column and subsequent book — even to colleagues at CNN, where he has a contributor contract. He left the Trump administration in June 2019 and endorsed Democrat Joe Biden for president this summer.

Trump and White House officials moved quickly to describe Taylor as someone with little standing and clout.

“This guy is a low-level lowlife that I don’t know. I have no idea who he is, other than I got to see him a little while ago on television,” Trump told a campaign rally crowd in Arizona. As he belittled Taylor as a “sleazebag” and called for his prosecution, the crowd broke into cheers of “drain that swamp.”

But as DHS chief of staff, Taylor was in many White House meetings with the president on his border policy and other major Homeland Security issues. During Taylor’s time as chief of staff, Trump threatened to shut down the border and his administration developed the policy to force asylum seekers to wait across the U.S.-Mexico border.

White House chief of staff Mark Meadows called Taylor’s revelation “a monumental embarrassment,” tweeting, “I’ve seen more exciting reveals in Scooby-Doo episodes.”

During a CNN appearance with Chris Cuomo Wednesday night, Taylor said he didn’t unmask himself earlier because the story would have disappeared within 48 hours.

“No one would pay attention and they wouldn’t care,” he said. “Right now, Americans are reviewing the president’s resume, his record and his character and it is mission critical that people like me, but others, come out now when the voters are listening and tell them who this man really is.”