Student who threatened Penn. high school had 1,600 rounds: police

April 3 (UPI) -- Pennsylvania police found more than 1,600 rounds of ammunition and a 9 mm handgun while searching the home of an 18-year-old exchange student accused of threatening an attack at his high school.

According to police, An Tso Sun, a student at Bonner Prendergast High School, used parts he bought online to build the gun himself.

Investigators said the 18-year-old foreign exchange student from Taiwan, who was arrested last week, had told a classmate at Bonner Prendergast High School not to come to school May 1 because he had planned a shooting spree that day. The classmate told a teacher, who called police.

According to Upper Darby, Pa., police, An's school-issued iPad showed he had searched at least 20 times how to buy an AK-47 or an AR-15 semi-automatic assault rifle and gun parts.

After getting a search warrant Tuesday, police said they went to the home of An's host family and found 663 rounds of 9 mm ammo, 425 rounds for an AK-47, nearly 300 for an AR-15 and 225 shotgun rounds. The hand-assembled gun had been removed from the student's room.

Police say An legally obtained all of the weaponry, which was discovered inside a duffel bag removed from his room prior to authorities arriving for the search.

"She immediately went to the bedroom" after she was contacted by authorities, said Upper Darby Police Supt. Michael Chitwood.

An was is being held on a detainer by U.S. Immigration and Customs Enforcement.