Police: Exchange student accused of shooting plot had over 1,600 rounds of ammunition

UPPER DARBY, Pa. -- Police say a foreign exchange student who was arrested on suspicion of threatening to shoot up his school had built a gun and had over 1,600 rounds of ammunition, CBS Philadelphia reports. An Tso Sun -- an 18-year-old foreign exchange student from Taiwan who was studying at Monsignor Bonner Archbishop Prendergast Catholic High School -- had hundreds of rounds for an AR-15, an AK-47 and a 9 mm handgun he built himself from parts purchased online. The parts are virtually untraceable. 

Sun was allegedly planning to unleash carnage on the school on May 1. Court records show he told a classmate about the possible attack, who in turn blew the lid off the plan once he alerted a school employee.

According to Upper Darby Police Superintendent Michael Chitwood, Sun had approximately 225 rounds of 12-gauge ammo, 663 rounds of 9 mm ammunition, 295 rounds of AR-15 ammunition and 425 rounds of AK-47 ammo, along with other sorts of ammunition.

During a news conference Monday, authorities revealed that a bag which had been in a bedroom in an East Lansdowne residence was moved in an attempt to hide it. 

"In my opinion, based on the totality of everything, we certainly feel he was going to shoot down the school," said Chitwood.

Student under arrest for threatening to attack Pa. school, police say

Chitwood said they are still conducting their investigation. Authorities are working to determine whether there were other people involved in the case. 

According to the Archdiocese, Sun has been expelled from the school. He has been charged with making terroristic threats and remains in police custody at this time. 

Sun's lawyers, Robert C. Keller and Michael N. Kotik, released a statement on behalf of their client that reads in part: "This young man has had no prior contacts with the courts and has been considered an affable, precocious student with no discipline or antisocial tendencies. The young man's parents have flown in from Taiwan and fully support their child. Our investigation reveals that there was no intention to terrorize or otherwise commit any criminal act." 

U.S. Immigration and Customs Enforcement officials have a detainer on Sun. 

The Department of Homeland Security will meet with police about the case on Tuesday.