Lawmakers on Capitol Hill are anxiously awaiting the release of a 500-page bombshell report prepared by Inspector General (IG) Michael Horowitz that will reveal whether the decision not to prosecute Hillary Clinton over her private email server was the right one.

The IG's office announced its decision to review the actions of the Justice Department and FBI — including those of then-FBI Director James Comey — ahead of the 2016 presidential election.

Comey announced in early July 2016 that, though he found he found Clinton was “extremely careless” in her handling of classified emails on a private server, the agency wouldn't recommend criminal charges be brought against her. But days before the election, Comey reversed course, announcing that the bureau would renew the investigation — a move Clinton believes cost her the election.

STAGE SET FOR BOMBSHELL IG REPORT ON CLINTON EMAIL CASE: WHO'S IN THE CROSSHAIRS?

Since then, Horowitz has interviewed dozens of U.S. officials, looked over more than 1 million records and reviewed the actions of several FBI and DOJ officials. Several top employees from those agencies are expected to come under fire in the IG report.

Supporters from both parties regard Horowitz, a former federal prosecutor appointed by President Barack Obama, as apolitical.

“Michael is very cautious,” Steven Cohen, a colleague of Horowitz’s in the southern district of New York's U.S. Attorney’s office, told Vanity Fair in February. “He’s dogged. He’s the opposite of a guy seeking to have a life in the limelight.”

“He is really one of the smartest and fairest people I have ever had the pleasure to work with,” Bill Hamel, former assistant inspector general for investigations at the Department of Education, echoed to The Hill. “He’s a straight shooter and a fair guy. He’s an honest broker.”

DOJ TO RELEASE LONG-AWAITED REVIEW OF CLINTON PROBE ON THURSDAY

The report was originally set to be released in May, but the date was pushed back. President Trump called for "transparency" in early June, demanding the IG release its findings.

“What is taking so long with the Inspector General’s Report on Crooked Hillary and Slippery James Comey. Numerous delays. Hope Report is not being changed and made weaker! There are so many horrible things to tell, the public has the right to know," Trump tweeted.

Here's what you need to know about Horowitz as the highly anticipated IG report is released to the public.

He worked in DOJ for more than a decade

Horowitz held positions within the DOJ from 1991 to 2002. The majority of his time was spent working as assistant U.S. Attorney for the Southern District of New York, where he served as chief of the Public Corruption Unit.

"In 1995, he was awarded the Attorney General’s Award for Distinguished Service for his work on a complex police corruption investigation," according to a Justice Department profile.

Four years later, he joined the DOJ's criminal division.

He graduated magna cum laude from Harvard Law

Horowitz graduated magna cum laude with a Juris Doctor degree (J.D) from Harvard Law School and a Bachelor of Arts, summa cum laude, from Brandeis University in Waltham, Massachusetts, his DOJ online profile states.

He oversaw the Fast and Furious case

Horowitz's most significant report before this one was the 2012 study of the botched Obama-era gun operation known as Fast and Furious.

Fast and Furious was a Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) operation in which the federal government allowed criminals to buy guns in Phoenix-area shops with the intention of tracking them as they were transported into Mexico. But the agency lost track of more than 1,400 of the 2,000 guns they allowed smugglers to purchase. Brian Terry, a border patrol agent, was killed in 2010 by an illegal immigrant with a weapon used in the failed operation.

The inspector general wrote the report just six months after he took over the position.

“It was just a remarkably intense first six months on the job. I know I wouldn’t have chosen to walk into the job that way. Looking back on it, it was sort of trial by fire. You sink or you swim pretty quickly, and fortunately I didn’t sink. People can use their own judgment about how well I swam," Horowitz told The Washington Post during a 2014 interview.



At the time, Horowitz considered his report a success, telling the Post it "addressed the issues people were looking for."

“It’s very important for any IG to have a strong professional relationship with the leaders of an organization. We have that. We meet separately roughly once a month with the deputy attorney general and try to make sure that they’re aware of problems that we’re finding within the organization that they have to manage," he added. "If there’s a problem that can be fixed, we want to fix it soon. We don’t want to have people wait for our report to fix it."

Fox News' Brooke Singman, Alex Pappas and The Associated Press contributed to this report.