A man believed to be a YouTube prankster who goes by the name “Arab Andy” was arrested Thursday after he livestreamed a fake bomb threat inside a classroom at the University of Washington in Seattle, police said.

Officials said the unidentified man entered the classroom holding up a cellphone and played a recording message that said: “C4 has been successfully activated. Bomb detonation countdown successfully started.”

Click on Detroit reported the YouTuber, who also goes by the name “ISIS Poseidon,” was recording his every movement on YouTube Live and Twitch. Police did not confirm the man was broadcasting live.

The occupants in the room fled the classroom before loud explosion noises were heard from the recording. The fire alarm was activated by somebody in the classroom before University of Washington Police responded to the scene, authorities said in a press release.

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Police arrested the man on charges of making a bomb threat and discovered in an investigation that it was a prank and “there was no device on him or left in the room. His name has not been released.

“We were in a reception in our conference room, listening to our chair talk about our year’s worth of stuff," a faculty member told The Daily, the school’s newspaper.

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"Then this man who was about six-foot-one comes in the doorway and says, ‘I’m sorry I’m late,’ and I didn’t recognize him, so I say, 'Are you supposed to be here?'" the staffer continued. The faculty member said the suspect played the fake bomb threat recording.

Students and faculty told Q13 Fox that they waited more than an hour to get the all-clear to head back inside the building.

The International Business Times reported “Arab Andy” has three YouTube channels with a few thousand subscribers. The subscribers can donate money to “Arab Andy” during his livestreams. YouTube removed the livestream from its website for violating its terms of service.