4 Fullerton schools locked down following hoax bomb threats

Five separate bomb threats forced the Fullerton Police Department to lock down four schools and evacuate a hospital on Thursday. 

The series of bomb threats began at about 1:25 p.m. when a caller claimed they planted explosives at Troy High School. As officers responded to the campus, the Fullerton Union High School received a similar threat about 24 minutes later.

Four minutes later, at 1:53 p.m., Sunny Hills High School received a bomb threat. As officers surveyed the situation at the three schools, Fern Drive Elementary School received another bomb threat at 2:20 p.m. 

Fullerton PD, with help from other agencies, responded to each campus with explosives-detecting canines. 

They did not find any explosive devices at the four schools. Roughly three hours after the bomb threat at Fern Drive, Fullerton police evacuated St. Jude Medical Center's emergency room at 5:40 p.m. following another bomb threat. 

At about 6:05 p.m., they allowed patients to return to the emergency room but continued their investigation. 

The Fullerton PD stated that detectives are attempting to determine the source of the calls. It is unclear if a single person was behind the string of threats.