A former Hawaii state worker who sent a false missile alert last month has said he is devastated for causing panic but was “100% sure” at the time that the attack was real.

The man in his 50s spoke to reporters on the condition that he not be identified because he fears for his safety after receiving threats.

He said an on-duty call that came in on January 13 did not sound like a drill. However, state officials said other workers clearly heard the word “exercise” repeated several times.

He said it felt like he had been hit with a “body blow” when he realised it was just a drill and he has had difficulty eating and sleeping since.

The Hawaii Emergency Management Agency fired him.

FCC Hawaii-Mistaken Missile Alert
A smartphone screen showing a false incoming ballistic missile emergency alert (Caleb Jones/AP)

The man’s superiors said they knew for years that he had problems performing his job. The worker had mistakenly believed drills for tsunami and fire warnings were actual events, and colleagues were not comfortable working with him, the state said.

His supervisors counselled him but kept him for a decade in a position that had to be renewed each year.

The ex-worker disputed that, saying he was not aware of any performance problems.

While starting a Saturday shift at the emergency operations centre in a former bunker in Honolulu’s Diamond Head crater on January 13, the man said, a co-worker took a phone call over the US Pacific Command secure line that sounded like a real warning, he said.

“When the phone call came in, someone picked up the receiver instead of hitting speaker phone so that everyone could hear the message,” he said.

The man said did not hear the beginning of the message that said, “exercise, exercise, exercise.”

“I heard the part, ‘this is not a drill’,” he said. “I didn’t hear exercise at all in the message or from my co-workers.”

Federal and state reports said the agency had a vague checklist for missile alerts, allowing workers to interpret the steps they should follow differently. Managers did not require a second person to sign off on alerts before they were sent, and the agency lacked any preparation on how to correct a false warning.

Those details emerged on Tuesday in reports on investigations about how the agency mistakenly blasted mobile phones and broadcast stations with the missile warning.

It took nearly 40 minutes for the agency to figure out a way to retract the false alert on the same platforms it was sent to.

“The protocols were not in place. It was a sense of urgency to put it in place as soon as possible. But those protocols were not developed to the point they should have,” retired Brigadier general Bruce Oliveira, who wrote the report on Hawaii’s internal investigation, said at a news conference.

Hawaii Emergency Management Agency administrator Vern Miyagi resigned as the reports were released. Officials revealed that the employee who sent the alert was fired on January 26. The state did not name him.

The agency’s executive officer, Toby Clairmont, said on Wednesday that he stepped down because it was clear action would be taken against agency leaders after the alert.

Another employee was being suspended without pay, officials said.