Schools across the nation were hit by a wave of robocall bomb threats Monday, closing buildings and forcing the evacuation of thousands of students, USA Today reports. Elementary, middle, and high schools in at least 18 states were targeted, and security expert Ken Trump says the automated calls seem to have all the signs of "swatting," hoax calls (often computer generated) meant to elicit a big response from law enforcement. Even schools in the UK were affected, with at least one receiving a warning that shrapnel from explosives would "take children's heads off," per the Independent. None of the threats were deemed credible, per NBC News.
Swatters likely aren't kids partaking in a simple, spur-of-the-moment prank. "Suspects are often more sophisticated," Trump says, adding that incidents like these have "skyrocketed" over the last few years. "They can use Voice over IP (VoIP) systems or other technologies that can be virtually impossible to track down." The AP notes that schools nationwide responded in various ways to the calls, with some shutting down completely and others reopening once authorities gave the all clear. "Every one of these may be swatting, [but] all it takes is one of them to be real and then we have a tragedy here," a Denver Public Schools spokesman tells CBS Denver. The FBI issued a statement noting the agency is "aware" of the threats and communicating with law enforcement, and that the public should "remain vigilant" and report anything that seems suspicious. (USA Today has a list of schools affected in each state.)