A new report from Fox News indicates that ex-Clinton IT staffer, Brian Pagliano, is proving to be a “devastating witness” in the FBI’s investigation of her secret e-mail server with the State Department.

As we reported last week, Pagliano, who pled the 5th to avoid cooperating with investigators, has been granted immunity in exchange for his story.

That revelation led Judge Andrew Napolitano to declare that Clinton “should be terrified of the fact that he’s been granted immunity.”

Napolitano claims that Pagliano being granted immunity means that Justice Department lawyers want to call him as a witness to testify “against some person or persons north of him on the totem pole.”

Now, his testimony is being called “devastating.”

Via Fox News:

Former Hillary Clinton IT specialist Bryan Pagliano, a key witness in the email probe who struck an immunity deal with the Justice Department, has told the FBI a range of details about how her personal email system was set up, according to an intelligence source close to the case who called him a “devastating witness.”

The source said Pagliano told the FBI who had access to the former secretary of state’s system – as well as when – and what devices were used, amounting to a roadmap for investigators.

“Bryan Pagliano is a devastating witness and, as the webmaster, knows exactly who had access to [Clinton’s] computer and devices at specific times. His importance to this case cannot be over-emphasized,” the intelligence source said.

The source, who is not authorized to speak on the record due to the sensitivity of the ongoing investigation, said Pagliano has provided information allowing investigators to knit together the emails with other evidence, including images of Clinton on the road as secretary of state.

According to the report, Pagliano’s statements have allowed investigators to fill in gaps in the e-mail history which they previously did not have access to.

At the Democrat debate this week, Univision’s Jorge Ramos asked Clinton “If you get indicted, will you drop out?”

Clinton refused to answer the question.