Investigators believe that a bomb threat that shut down Manchester-Boston Regional Airport for hours last year was called in by a real person rather than made by a robocall.News 9 Investigates obtained a copy of the call, as well as documents detailing the steps police took to track down the person behind it."I have planted a bomb on plane NK 2025 going to Tampa at 11:25 a.m.," the caller told a dispatcher."And where did you put the bomb?" the dispatcher asked."I ain't telling you that (expletive)," the caller said. "You got to find it."The caller told dispatchers that his name was "Jack Burns." >> Download the free WMUR app to get updates on the go: Apple | Google Play <<Documents obtained by News 9 Investigates show that Londonderry police believed the caller was an actual person, not a robocall, because of his Southern accent, inflection and immediate responses to the dispatcher's questions. Detectives also believe the call was made from an Android device. IP addresses for a person named Jack Burns were connected to internet service providers in Australia.The caller claimed that the bomb was going to explode five minutes into the flight. After the threat came in, the airport was evacuated and shut down for several hours.Investigators used K-9s to search the plane and nearby terminals but said no devices were found.No suspects have been publicly identified. The FBI declined to comment.