The Pacific archipelago, already on edge over the threat posed by North Korea, was terrorized by the erroneous alert, which was sent out by phone to residents and tourists and remained uncorrected for nearly 40 minutes.
Another employee of the state agency, which is responsible for notifying the public of threats to their safety, has been suspended, Major General Joe Logan, the state adjutant general, told reporters in Hawaii.
HEMA administrator Vern Miyagi resigned on Tuesday to take responsibility for the January 13 incident, Logan said, and the emergency warning officer who sent out the alert of an imminent ballistic missile attack was fired on Friday.
A state investigative report released on Tuesday said that the fired employee had been a "source of concern" for 10 years because of his "poor performance."
"He is unable to comprehend the situation at hand and has confused real life events and drills on at least two separate occasions," the report said.
In a separate report, the Federal Communications Commission (FCC) said the officer claimed he believed the threat was real and had not heard a phrase stating that it was an exercise.
At the same time, the report said, the sentence "This is not a drill" was included in the recorded message which prompted the officer to issue the alert.
Mobile phones across the Pacific islands received the emergency alert around 8:07 am and it was also transmitted by television and radio stations.
"In the minutes that followed, panic-stricken citizens called their families to say what they believed were their last words, and some even resorted to jumping into manholes to find shelter," FCC chairman Ajit Pai said in a statement accompanying the report.
The erroneous message came amid tensions with North Korea, which has tested rockets powerful enough to reach the United States, though it is unclear whether they are yet able to deliver nuclear payloads.
'Exercise, exercise, exercise'
It took the authorities 38 minutes to send out a message cancelling the false alert and the FCC also looked into why it took so long to do so.
The FCC and state investigators blamed the mistake on a combination of human error, insufficient management controls and poor computer software.
The overnight-shift supervisor informed the day-shift supervisor of the plan but the day-shift supervisor understood the drill was for the overnight workers ending their shift not for his arriving staff.
"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 FCC report said.
It said the overnight-shift supervisor called the day-shift warning officers at 8:05 am pretending to be from US Pacific Command.
A recorded message was played over the phone which began and ended with the words "exercise, exercise, exercise."
The message, however, also included the phrase "This is not a drill" used for an actual live ballistic missile alert, the report said.
Three day-shift warning officers listened to the recording on speakerphone and one of them "believed that the missile threat was real" and issued a live alert at 8:07 am after hearing the sentence "This is not a drill," it said.
The officer declined to be interviewed by the FCC but said in a written statement to HEMA that he did not hear the phrase "exercise, exercise, exercise."
"Other warning officers who heard the recording in the watch center report that they knew that the erroneous incoming message did not indicate a real missile threat, but was supposed to indicate the beginning of an exercise," the report said.
"Because we've not been able to interview the day shift warning officer who transmitted the false alert, we're 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 (as opposed to believing that it was a drill and accidentally sending out the live alert)," it added.
The FCC was also critical of HEMA's failure to develop "standard procedures" to cancel a false alert and said "the error was worsened by the delay in authoritatively correcting the misinformation."
In the future, the FCC said, supervisors will receive advance notice of all drills and two warning officers will validate alerts instead of one.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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