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PHILADELPHIA (CBS) – The teenager who authorities say plotted to shoot up a Delaware County school has been sentenced after entering an open guilty plea to terroristic threats on Monday.

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Authorities say An Tso Sun, 18, of Taiwan, allegedly told a fellow student not come to school on a particular day because he was going to be shooting up Monsignor Bonner and Archbishop Prendergast High School in Drexel Hill.

Credit: (CBS3)

According to investigators, Sun stockpiled more than 1,600 rounds of ammunition and planned to shoot his fellow classmates on May 1.

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“He was planning something horrible,” said Upper Darby Police Superintendent Michael Chitwood after his arrest in March.

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On June 4, a judge sentenced Sun to four to 23 months in the George W. Hill Correctional Facility and to be paroled to the ICE detainer. He also was ordered to pay $700 in restitution, $350 each to Folcroft Police Department and Trainer Police Department for K-9 services.

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The story has made international news as Sun’s parents are celebrities in Tawian. His father had a talk show and his mother is an actress.