An Tso Sun is an exchange student from Taiwan residing in Upper Darby, Pennsylvania. ^{[undefined] [undefined] [1]}

Sun came from Taiwan on a 5-year student visa in July 2017. He was hosted by the family of a Pennsylvania attorney and enrolled at Monsignor Bonner and Archbishop Prendergast High School in Drexel Hill for his senior year. ^{[undefined] [undefined]}

Sun already been accepted to a U.S. university and had planned to major in criminal justice. ^[undefined]

On Tuesday March 27, 2018, Sun was arrested on a terroristic threat charge for allegedly threatening to attack his high school. On Wednesday March 28, 2018, Upper Darby police hauled the ammo, crossbow, ski mask and gun-making components they found in Sun’s room. ^{[undefined] [undefined]}

He told a fellow student, 'Don't come to school on May 1 because I'm going to shoot up the school,' and then he said, 'I'm kidding,'".

^[1]