The webmaster who set up Hillary Clinton's personal email server – and is now giving the FBI a road map on its use — is a "devastating witness" in the probe that's dogged the Democratic presidential front-runner.IT specialist Bryan Pagliano,, is providing details of who had access to the former secretary of state's system, and when,"Bryan Pagliano is a devastating witness and, as the webmaster, knows exactly who had access to [Clinton's] computer and devices at specific times," an unnamed intelligence source tells Fox News. "His importance to this case cannot be over-emphasized."The source tells Fox News that Pagliano's information allows the FBI investigators to cross-reference emails with other evidence that will help pinpoint potential gaps in the record."Don't forget all those photos with her using various devices and it is easy to track the whereabouts of her phone," the source tells Fox News. "It is still boils down to a paper case. Did you email at this time from your home or elsewhere using this device? And here is a picture of you and your aides holding the devices."An unnamed source close to Pagliano downplays the webmaster's role, saying he met with the FBI on a "limited basis" and was a "peripheral" player in the investigation.Fox News also reports that Clinton's repeated insistence that she neither sent or received any material marked classified at the time she was using the email server allegedly is misleading — noting classification is based on content rather than markings.The intelligence source tells Fox News the FBI is "extremely focused" on the 22 "top secret"to national security to publicly release, with agents reviewing those sent by Clinton as well her subordinates including former chief of staff Cheryl Mills."Mrs. Clinton sending them in this instance would show her intent much more than would receiving [them]," the source tells Fox News."Hillary Clinton was at a minimum grossly negligent in her handling of NDI [National Defense Information] materials merely by her insisting that she utilize a private server versus a [U.S. government] server. Remember, NDI does not have to be classified."