Documents given to the Senate Judiciary Committee suggest that James Comey had made up his mind to clear Hillary Clinton well before the FBI investigation was finished .
According to the unredacted portions of the transcripts, it appears that in April or early May of 2016, Mr. Corney had already decided he would issue a statement exonerating Secretary Clinton. That was long before FBI agents finished their work.
https://www.judiciary.senate.gov/imo...Statement).pdf

Comey prepared the draft exoneration for Evita ,before conducting interviews with top Clinton aides who were offered immunity for their cooperation .Included were Bryan Pagliano, who set up the personal server where Evita hosted and shared top secret information, and Chief of Staff Cheryl Mills .Comey distributed his draft inside the FBI in May 2016 .How that influenced the investigation is anyone's guess.

According to Newsweek ;Justice Department veterans from both Democratic and Republican administrations said Comey’s actions strayed from agency rules and norms. The Justice Department’s Office of the Inspector General launched a review of his conduct, and Deputy Attorney General Rod Rosenstein wrote in a memo to Trump before Comey’s firing, “Almost everyone agrees that the director made serious mistakes; it is one of the few issues that unites people of different perspectives.”

Did James Comey Break Rules by Drafting Hillary Clinton Statement? FBI Experts Are Divided