UPDATE:
The Fortuna Police Department sent out a press release this evening stating that it has investigated additional reports of violent social media threats since Thursday and found them not to be credible.

Since officials thwarted two students’ alleged plans to set off numerous homemade chemical bombs during an all-school assembly Thursday, FPD has been working with the FBI and the U.S. Attorney’s Office on the case, according to a press release. Additionally, there will be a “strong law enforcement presence” at the school Monday as a precaution and to help “allay any fears that students, staff and parents may have following Thursday’s arrests.

See the full press release copied at the bottom of this post.

PREVIOUSLY:
According to Police Chief Bill Dobberstein, three short hours is all that stood between Fortuna High School and tragedy.

Fortuna police announced last night that they had arrested two male 15-year-old students at the school who had been planning a “mass casualty event” to take place during an all-school rally on campus yesterday afternoon.

“It could have been a terrible tragedy if that rally would have taken place,” Dobberstein told the Journal this morning. “The whole school was going to be there for this thing.”

The police chief said word of the plot — which the suspects had been planning for some time — came to school administrators’ attention around noon yesterday. Dobberstein said one of the suspects in the case had apparently texted a friend, telling him or her to “basically stay out of the gym during the rally.” The friend then told another student, who told another student, who told his or her mother, who called another mother who ultimately called the school and made them aware of the warning, according to Dobberstein.

Fortuna High School Principal Clinton Duey was then able to trace the origins of the warning back to one of the suspects, and brought him into his office. Duey was able to get the other suspect's name, Dobberstein said, and brought him into the office as well, holding both suspects there while he called police.

Dobberstein said his department was notified of the situation at about 1:15 p.m. and responded immediately to the school. “It was literally about an hour before the school was scheduled to go to the rally,” Dobberstein said.

The chief said officers searched the students and, in one of their backpacks, found “several components for making some kind of toxic chemical gas explosion devices.” The students were missing a “key ingredient,” Dobberstein said, but police believe they had the missing chemical stashed somewhere on campus, based on witness statements and messages found on the suspects’ phones, tablets or computers. It appears the suspects were planning on making multiple explosive devices with a substance akin to homemade mustard gas, or sulfur mustard, a chemical agent that causes severe burning of the skin, eyes and respiratory system.

“Absolutely more than one,” the chief said. “They had enough material to definitely make more than one.”

Dobberstein said investigators will be serving search warrants today, including one to gain access to “electronic messaging devices” used by the suspects. But the chief said that based on what police have accessed thus far, it appears the suspects may have been planning a mass casualty event for some time and targeting “when there was going to be a large gathering of students and teachers in one place.”

So far, police don’t have any reason to believe anyone else was involved in the plot, Dobberstein said, but can’t rule out the possibility. Both suspects were arrested yesterday and booked into juvenile hall.

As to a motive for the thwarted attack, Dobberstein said many have been “thrown around, but we couldn’t say with certainty what the motive was at all.” The chief said he doesn’t believe either of the suspects had a lot of prior police contact, but otherwise wouldn’t comment on the boys. He also said it doesn't appear either of the suspects had access to other weapons.

Fortuna High School administrators didn't immediately respond to messages this morning.

The case remains under investigation by the Fortuna Police and the Humboldt County District Attorney’s Office, and police ask anyone with information to contact the police department at 725-7550.

Dobberstein commended the response of students and parents who relayed information, and of administrators who quickly identified and detained the suspects.

See the full press release from FPD copied below:

Fortuna Police Investigate threat to Fortuna High School

On November 10, 2016 at about 1:15 PM the Fortuna Police Department responded to the Fortuna High School for a report of a threat to student safety.

Officers contacted two 15 year-old students that had been detained by high school staff. Officers learned the two juveniles were communicating with each other, planning a mass casualty event that was to take place at a rally at FUHS later in the afternoon. Officers located some components for making an explosive device, however incomplete, in the possession of one of the juveniles. Evidence and items located on the juveniles indicated the threat was very serious in nature.

The two juveniles were taken into police custody and later transported to Juvenile Hall. The Fortuna Police Department is working this investigation with investigators from the Humboldt County District Attorney’s Office. This is a very active investigation with multiple locations being searched.

The Fortuna Police Department asks the public for any information and assistance in this case. Anyone with any information is asked to contact the Fortuna Police Department at (707) 725-7550.

From FPD Saturday:

Fortuna High School threats case update

The Fortuna Police Department is continuing our investigation on the threats reported to us on Thursday afternoon, involving two students who reportedly had the intention to commit an act, or acts of mass violence at Fortuna High School’s Pep Rally, scheduled for that afternoon.

Both individuals were arrested, and found to have items in their possession which lent credibility to those threats.

We have also become aware of further allegations of planned violence on social media by other individuals. These allegations and reports are being taken very seriously and have been followed up by investigating officers. These allegations have been found to not be credible.

However, our department continues to work closely with the Federal Bureau of Investigation and the US Attorney’s office on this investigation.

As an added precaution, there will be a strong law enforcement presence at the High School on Monday to help allay any fears that students, staff and parents may have following Thursday’s arrests.

As more information becomes available to us as result of this investigation, we will provide pertinent facts to help dispel any unfounded rumors being circulated on social media and by other means.

We ask that citizens call the department, at 725-7550, with any information that they may have regarding Thursday’s incident, or any rumors regarding any threats to students or other citizens.