UPDATE: Penn State cops bust student in YikYak threat to 'kill everyone'

UPDATE: Penn State says it arrested an unnamed 20-year-old student at the school's main campus and plan to charge him for threatening to bring assault rifles to school and "kill everyone."

Police said the student, who lives off campus, told them it was just a "prank," but Penn State police chief Tyrone Parham said in a statement that "alarming an entire community is not considered a joke," and "this individual will be held accountable."

EARLIER: Penn State University police "will have an increased presence" at the Hub, the State College campus's student center and food court, after students reported an anonymous Saturday night social-media post threatening a shooting attack.

The note appeared on Yik Yak, an anonymous student-focused social-media app based in Atlanta and one of a number of services that have arisen in competition with mainstream social media like Facebook.

Police, the FBI and Yik Yak are cooperating "to determine the origin and author of the threat," Penn State spokeswoman Lisa Powers told the Inquirer. Yik Yak did not immediately return a message seeking comment.

"While this threat is anonymous and we cannot yet determine its credibility, all threats are taken seriously and police are working vigorously on determining its origin and its validity," added Powers. She said Penn State "activities have not been canceled and are expected to proceed as normal."