SEATTLE – Police arrested a 16-year-old Seattle student this week after he allegedly brought a Molotov cocktail in his backpack to a high school located in the Seattle City Armory building downtown.

Officers called in the bomb squad and evacuated the building as a precaution Monday morning after arresting the student based on a tip from another student. Authorities allegedly found the suspect with a Molotov cocktail – a bottle filled with flammable liquid – in his backpack at The Center School, a public arts-focused high school at Seattle Center, the Seattle Times reports.

The teen was arrested for possession of an incendiary device and booked into the King County Youth Service Center. Police said they believe the student was the only person involved, and that he did not make any specific threats to teachers or other students, according to the news site.

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Authorities evacuated the Seattle Center Armory building and searched the premises with bomb dogs to ensure there were no other explosives.

“Students waited in a parking lot outside for about an hour before classes were called off,” the Times reports.

The evacuation affected The Center School and the Academy for Interactive Entertainment, a video gaming school, as well as businesses located in the same building.

When the fire alarms went off, student Nathon Hampton said everyone casually walked out of the building as if it was a typical fire drill.

“Everybody was calm,” he said.

Police reopened the building to the public around 12:45 p.m.

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On Tuesday, Seattle Public Schools officials placed the high school’s principal, Oksana Britsova, on paid administrative leave while they investigate. They put retired principal BiHoa Caldwell in charge “while the district reviews whether all protocols were followed during Monday’s incident,” according to the news site.

The district sent a letter to parents informing them of the incident, and how the school’s staff “effectively implemented their emergency plan,” the Times reports.

Authorities said they remain unsure of the student’s motive for bringing the explosive to school.