One student's online "prank" ended Sunday evening with a knock at the door, a confession and an arrest on charges of terroristic threats.

Jong Seong Shim, who posted the HUB shooting threat on the anonymous social media app Yik Yak this weekend, was "surprised" when Penn State Police showed up shortly after 9 p.m., Penn State Police Chief Tyrone Parham said at a press conference Monday afternoon outside the university police station.

Shim, a 20-year-old sophomore from Tinton Falls, New Jersey, was arraigned Monday and charged with misdemeanor counts of terroristic threats and disorderly conduct, Penn State spokeswoman Lisa Powers said via email.

When asked if Shim would be expelled, Parham said he did not know of Shim's status as a student.

Shim posted the message on Yik Yak Saturday night. In the post, he threatened to perpetrate a shooting at the HUB Monday at noon, Powers said. Shim called the threat — to “kill everyone in Penn State main” — a "prank."

Police found no weapons in a search of Shim’s Vairo Boulevard residence, Parham said, but he could not speak to whether any weapons were registered to Shim's name.

Police were prepared to have a large presence at the HUB Monday. And even after Sunday's arrest, additional officers were stationed there today, Parham said.

At about 9 a.m. Sunday morning, police were tipped off to the threat by a student who had seen the post and took a screen shot of it before it was taken down from the app. Police thought the post might be a joke, Parham said, but took it seriously nonetheless.

Officers remained on "high alert" Sunday evening as they alerted the regional FBI office and the State College Police Department. They worked with Yik Yak officials to locate Shim and the mobile device used to post the threatening message.

Shim told police he did not mean to cause harm or a commotion, Parham said.

Shim was being held at Centre County Correctional Facility Monday since he did not post his $100,000 bail, Powers said.

“We are grateful to our very alert and diligent students who first discovered this threat and raised their concerns with police,” Steve Shelow, Penn State’s assistant vice president for Police and Public Safety, said in a press release. “It is quick reporting by observers and strong cooperation among law enforcement agencies that allowed us to move swiftly to identify and apprehend the suspect.”

Parham said police have experienced issues with Yik Yak posts referencing deaths or injuries before, but nothing this serious.

Shim's next hearing is scheduled for 8:30 a.m. on Oct. 22 at the Centre County Courthouse in Bellefonte, Powers said.

Read Tuesday's edition of The Daily Collegian for more information.