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‘Lone Wolf?’: Department of Homeland Security Investigating Taiwanese Exchange Student

He quietly built an arsenal in Delaware County. Now, the Department of Homeland Security is helping local officials unravel what led a Taiwanese exchange student to allegedly make terroristic threats against his host high school.

On Tuesday, Upper Darby police turned over a computer, iPad and smartphone belonging to An Tso Sun to Homeland Security for analysis, Upper Darby Police Department Superintendent Michael Chitwood told NBC10.

The federal agency will determine whether Sun’s threats to carry out a shooting at Bonner and Prendergast Catholic High School in Drexel Hill expand beyond local boundaries.

“Is this a lone wolf or is he associated with somebody else?” Chitwood asked. “We’ll have a better idea when we get everything in place.”

Sun remains jailed after being charged last week with making terroristic threats. His parents traveled to the U.S. from Taiwan over the weekend, but declined an interview with NBC10. 

Their 18-year-old son has only been in the U.S. for five months, according to police. He threatened to commit a shooting on May 1 at the high school he attended, according to Upper Darby police. Sun later claimed to have been joking.

But investigators this week discovered 1,600 rounds of ammunition for a variety of firearms, including assault rifles and handguns. The ammo and gun parts were bought over the internet since Sun arrived to the United States in August, Chitwood said. He went online on a school-issued iPad at least 20 times to search about guns or to buy ammo and gun parts.

During a search of Sun's bedroom on Tuesday, police recovered other items including a military-style ballistic vest, military-style web gear with pouches to hold ammo clips, a crossbow with scope and seven arrows, a loading dock for rifle clips, 9-mm ammunition and a strangling device, police said.

During the course of the investigation, Chitwood said police found the duffel bag.

Sun, who is in the U.S. on a student visa, legally obtained all of the weaponry, Chitwood said. His mother is a famous opera singer in Taiwan and his father is an actor. 

"People in Taiwan are just as shocked as they are here," John Zang, a CTI-TV reporter, said. "His parents are like Brad and Angelina."

Sun's tutor described him as a "kind" teen who "really cared about things." 

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