WASHINGTON, D.C. — President Donald Trump announced Wednesday that he would pick Christopher Wray, a former Justice Department official who also has represented New Jersey Gov. Chris Christie, to lead the FBI.

The announcement on Twitter, which caught many in Washington off guard, appeared to be an effort to seize attention ahead of what is expected to be blockbuster congressional testimony from former FBI director James Comey, who is scheduled to appear before the Senate Intelligence Committee on Thursday.

Trump called Wray “a man of impeccable credentials” and promised that details of the announcement would follow.

The use of Twitter to make the high-profile announcement solidified the social media tool’s role as Trump’s primary mode of public communication, despite some concern from fellow Republicans. Trump insisted defiantly this week that Twitter remains his best tool to deliver unfiltered news to his supporters.

Wray, who earned undergraduate and law degrees from Yale University, first became a federal prosecutor in 1997, in the Northern District of Georgia, according to his Justice Department biography. He came to Washington in 2001 to become an associate deputy attorney general in the George W. Bush administration, rising to assistant attorney general in charge of the criminal division in 2003, a job he held for two years.

Now in private practice, he represented Christie amid the “Bridgegate” scandal in which two of the governor’s top aides were convicted of creating a massive traffic jam at the George Washington Bridge as political payback against a mayor who declined to endorse Christie in his presidential bid.

The job became vacant after Trump fired Comey amid his investigation into Russian meddling in the 2016 campaign and potential collusion with the Trump campaign.