(Adds police find no explosive materials in "dummy" device)
By David Schwartz
PHOENIX, May 6 (Reuters) - A 16-year-old boy suspected of threatening to attack his school was arrested on Tuesday at his suburban Phoenix home, where officers found what they first suspected was an explosive device and evacuated both his school and part of his apartment complex, police said.
The unidentified student at Chief Hill Academy in Chandler, Arizona, is accused of making a threat via text message to another student, Chandler police spokesman Detective Seth Tyler said.
Tyler said the threat was made on Tuesday morning at the boy's school, which has about 200 children in grades 7 through 12, and was conceived as a "mass casualty type event."
When officers arrested the boy, they found what they believed could be an explosive device inside his apartment, Tyler said. He said a bomb squad was called in from another police department and it was later determined to be a "dummy device" made to look like a bomb but containing no explosive materials.
The school was evacuated because police suspected there may be additional explosive devices there, but none were found, Tyler said. (Editing by Alex Dobuzinskis and Grant McCool)