In a one-hour period Thursday morning, five bomb or shooting threats were called in to five schools in five different cities: Boise, Kuna, Caldwell, Nampa and Twin Falls.
During a 15-minute period Thursday afternoon, bomb threats were called in to three Eagle Road businesses.
Law enforcement officers responded and determined that all the threats were unfounded.
The calls could have beenstudent pranks to try to get out of Thursday's high school ISAT tests; copycats inspired by earlier threats; or something more nefarious such as a law enforcement diversion test, officials said.
As soon as officials became aware of the multiple threats, Caldwell Police Chief Chris Allgood said, they "started having that conversation."
Allgood said a timed series of diversions or a large-scale diversion is something that "has kind of been at the forefront of all of our minds for a very long time. Today was a surprise, but when it came, we were ready to respond."
For example, Caldwell police immediately sent officers to Caldwell High and other schools to make sure they were secure, and other officers, assisted by Canyon County sheriff's deputies, stepped up patrols elsewhere in the city.
That ensured no area was without coverage if the call turned out to be a diversion or if another unrelated emergency occurred, Allgood said.
Boise police responded similarly. Officers are trained to treat such a call as both a serious threat and a possible diversion and respond accordingly, said spokesperson Lynn Hightower. Agencies work together to back up or beef up each other's efforts.
Even if Thursday's calls turn out to be pranks, authorities won't treat them like one, Hightower said.
Such threats of violence are a felony, chargeable to juveniles or adults and punishable by up to five years in prison.
"Just making the call is a felony. Just writing the note is a felony," Hightower said.
Crime Stoppers is offering a $1,000 reward for information leading to the arrest of the people responsible. Anyone with information is asked to call 343-COPS (2677).
Cynthia Sewell: 377-6428, Twitter: @CynthiaSewell