An 18-year-old student has been arrested for making a threat against a Delaware County high school.

An Tso Sun, of Taiwan, was arrested Tuesday night for threatening to shoot up Bonner Prendergast Catholic High School.

Police say Sun had searched how to purchase an AK-47 and AR-15 online. Authorities also learned that in February, Sun had brought in a high caliber bullet into school. Sun also showed a video of him with a flame-thrower in mask, according to police. Police have not yet obtained the footage in question but say they believe Sun was planning an attack.

Sun later claimed he was joking about the alleged threat against the school.

"Kudos to the person who stepped forward and helped to avert a tragedy," Upper Darby police tweeted.

Upper Darby Police Superintendent Michael Chitwood unveiled what authorities found at Sun's residence, including a military-style ballistic vest, a web gear backpack with pouches to hold ammo clips, a type of cold weather gear, a high-powered crossbow with scope and light and seven arrows, a loading dock--or 'speed loader'--meant for holding AK-47s and AR-15s, a wooden box made for a homemade gun, 20 live rounds of 9mm ammunition, a military ski mask, ear protectors and a garrote which Chitwood describes as "a strangling device."


Sun, who is in the United States on a student visa, is currently being held at Delaware County Prison on $100,000 bail.

This is a developing story. Stay with FOX 29 for updates.