"The employee said it looked like a pipe bomb. He took it off the roof not too sure why he did that but police were then notified," Davis School District spokesman Chris Williams said.
Horton said the employee originally took the device into the school, but by the time police arrived, the pipe bomb had been taken to the school's parking lot.
The school, located at 2025 E. 3100 North, was evacuated of students and staff while officers inspected the school grounds. In all, 700 students along with 70 teachers and other school staff were safely evacuated to a nearby LDS church.
Layton police and firefighters, as well as the Davis County Sheriff's Department bomb squad responded to the scene, Williams said. Two bomb-sniffing canine units from Hill Air Force Base also assisted.
Horton said bomb squad technicians broke apart the pipe bomb using a water gun device. Bomb-sniffing dogs and police authorities also checked out the school, Horton said, and no other threats were found. Classes were expected to resume Tuesday.
It is unclear how long the pipe bomb was on the roof, but Horton said a worker reported he was on the roof on Friday and didn't see the device.
Other schools in Davis School District also were to be searched for threats. A suspicious backpack was reported at Northridge High School on Monday afternoon, but Horton said the pack was X-rayed and found to contain just school supplies.
Tribune reporter Kimball Bennion contributed to this story.