Tempe Police arrested Joshua Prater, a senior at Marcos de Niza High School, for misconduct involving weapons and possession of a prohibited weapon and an improvised explosive device. Prater told police he had made the devices several years ago.
Wednesday morning, police said it didn't appear Prater had planned to set off any of the devices.
According to police, at 2:30 p.m. Tuesday, a housekeeper found a device that looked like a bomb in Prater's bedroom and immediately took it to a fire station on McClintock Drive near Baseline Road.
After investigating the device, the fire department notified police and an explosive ordnance disposal unit was called to the scene.
"When our bomb squad got out there, they got an X-ray and looked inside," said police Sgt. Mike Pooley. "They indeed said it was a valid IED. ... It was something that could have seriously hurt somebody, in fact killed them."
The IED was disabled at the scene.
The housekeeper also alerted police that she found more materials at the residence, located on the 1600 block of East Candlestick Road. Detectives spent the evening searching the area for more devices and related materials.