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The emergency management worker who sent a false missile alert that led to a terrifying 38 minutes for Hawaii earlier this month said the worker believed the threat was real, according to a preliminary federal investigation.

“A combination of human error and inadequate safeguards contributed to this false alert,” the Federal Communications Commission said in remarks on the preliminary report released Tuesday.

The FCC report laid out a detailed timeline of the miscommunication that led to the transmission of the ballistic missile alert on Jan. 13, which sent some scrambling to seek shelter amid an increased threat from North Korea.

Later Tuesday, officials releasing results of the state's internal investigation announced that the head of Hawaii’s Emergency Management Agency, Vern Miyagi, had "taken full responsibility" for the incident and resigned Tuesday morning.

The employee who sent the false alert was terminated, officials said. Earlier this month, authorities said that worker had been "reassigned."

Another staffer resigned before any disciplinary action was taken, and the agency was in the process of suspending another employee without pay, state Adjutant General Maj. Gen. Joe Logan said at a news conference.

The morning of the false alarm, the midnight shift supervisor at the Hawaii Emergency Management Agency decided to conduct a spontaneous ballistic missile defense drill during the transition to the day shift, according to the FCC report.

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At around 8 a.m. local time (1 p.m. ET), the midnight shift supervisor informed the dayshift supervisor about the plan to conduct that drill, but the incoming supervisor believed it was only for the midnight shift officers — not the officers about to begin, according to the report.

“As a result, the day shift supervisor was not in the proper location to supervise the day shift warning officers when the ballistic missile defense drill was initiated,” the report said.

The midnight shift supervisor initiated that drill at around 8:05 a.m., pretending to be the U.S. Pacific Command and playing a recorded message over the phone to the day shift officer, according to the report.

The recorded message began and ended with the phrase “exercise, exercise, exercise,” according to the report, but also featured language scripted for use during an actual live ballistic missile test alert, including the sentence, “This is not a drill.”

Cars drive past a highway sign that reads "MISSILE ALERT ERROR THERE IS NO THREAT" on the H-1 Freeway in Honolulu on Jan. 13, 2018 Cory Lum / Civil Beat via AP file

The day shift worker who sent the alert wrote in a statement that he heard the “this is not a drill” portion and not the parts indicating it was an exercise, according to the report. The worker wrote that he therefore “believed that the missile threat was real,” according to the report. Two minutes later, that officer transmitted the live incoming missile alert to the state of Hawaii.

While the officer provided a written statement to officials, the FCC has thus far not been able to interview him and was “not in a position to fully evaluate the credibility of their assertion that they believed there was an actual missile threat and intentionally sent the live alert,” the report said.

An FCC official said Thursday that the worker, who has not been publicly identified, was not cooperating with the investigation.

During the news conference Tuesday, officials reiterated that the male worker said he did not know it was a drill even though five others had heard the portion of the message indicating it was an exercise.

That worker had "a history of confusing drill and real world events" on at least two prior occasions, said Retired Brig. Gen. Bruce Oliveira, who led the internal investigation.

Throughout the employee's tenure "there have been reports" of performance issues and he had confused practice drills once during a fire incident drill and another time during a tsunami incident drill, Oliveira said. The employee was terminated on Friday, officials said.

The FCC said in its findings that the missile threat drill was “run without sufficient supervision” and that “there were no procedures in place to prevent a single person from mistakenly sending a missile alert to the State of Hawaii.”

“While such an alert addressed a matter of the utmost gravity, there was no requirement in place for a warning officer to double check with a colleague or get signoff from a supervisor before sending such an alert,” the report said.

Once the false alert was sent, the error was “worsened by the delay in authoritatively correcting the misinformation,” according to the report.

In a statement on the preliminary report, FCC Chairman Ajit Pai said the “two most troubling things" found by the investigation were that the emergency management agency did not "have reasonable safeguards in place to prevent human error from resulting in the transmission of a false alert” and that they “didn’t have a plan for what to do if a false alert was transmitted.”

“The public needs to be able to trust that when the government issues an emergency alert, it is indeed a credible alert,” he said. “Otherwise, people won’t take alerts seriously and respond appropriately when a real emergency strikes and lives are on the line.”

The comments on the report noted that Hawaii's emergency management agency had already taken steps to "ensure that an incident like this never happens again."

Those included a new policy that supervisors must receive advance notice of all future drills, requiring two credentialed warning officers to sign in and validate the transmission of every alert and test, a false alert correction template, software improvements and stopping all future ballistic missile defense drills pending conclusion of its own investigation, according to the report.