Anti-extremism researchers say they have identified a group claiming responsibility for the hoax active-shooter calls that led to massive police responses and widespread panic at Villanova University and other colleges as students returned to campus last week. Members of the nonprofit Global Project Against Hate and Extremism (GPAHE) said Wednesday they believe the source of the calls is a group dubbed Purgatory, part of an online threat network called “The Com” that exists at the “intersection of extremism, cybercrime, child abuse, and violence,” according to the nonprofit, which was formed in 2020 by former members of the Southern Poverty Law...