Police: School shooting plot suspect had 1,600 rounds of ammo

An exchange student in southeast Pennsylvania charged with making terrorist threats against his high school was found to have over 1,600 rounds of ammunition and multiple weapons stashed at his home, police say. 

Eighteen-year-old An Tso Sun, an exchange student from Taiwan studying at a Philadelphia-area high school, had a stash that included 663 rounds of 9 millimeter ammunition for a handgun he built himself; 295 rounds of AR-15 ammunition and 425 rounds for an AK-47, according to the Upper Darby Police Department, CBS News reports.

The police are currently investigating whether Sun, who remains in custody, was planning to attack Monsignor Bonner Archbishop Prendergast Catholic High School on May 1.

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Sun reportedly warned a 17-year-old classmate not to come to school that day. The classmate told a school employee, who then alerted the police department. Sun was arrested the same day after speaking with a detective, according to The Philadelphia Inquirer

Upper Darby Police Superintendent Michael Chitwood said Monday that he and the force "certainly feel" Sun had the intention of carrying out the attack. 

Police are also investigating whether anyone else was involved in the plot, after it was discovered the handgun and 9mm ammunition had been moved from his room after authorities alerted a host parent in the house. 

U.S. Immigration and Customs Enforcement has barred Sun from receiving bail. Detectives involved with the case are set to meet with the Department of Homeland Security on Tuesday.