President Trump on Friday accused James B. Comey, the FBI director he abruptly fired in May, of exonerating Hillary Clinton before his agency’s probe into her private email server was complete, taking to Twitter to charge there is “rigged system.”

“Wow, looks like James B. Comey exonerated Hillary Clinton long before the investigation was over . . . and so much more,” Trump wrote in a morning tweet Friday. “A rigged system!”

The president seemed to be referring to a letter Sens. Lindsay O. Graham (R-S.C.) and Charles E. Grassley (R-Iowa), both members of the Senate Judiciary Committee, sent to FBI Director Christopher A. Wray on Wednesday.

In their letter, the senators wrote they had recently reviewed transcripts from interviews the Office of Special Counsel conducted last fall with FBI officials as part of its inquiry into Comey’s handling of the Clinton investigation. The Office of Special Counsel is not associated with Robert S. Mueller III, the special counsel investigating Russian interference in the 2016 election, but an independent agency that investigates violations involving federal employees.