The incident follows a much bigger alert that had residents of Hawaii extremely concerned: in January, they were warned of a ballistic missile headed their way. It caused more than a half an hour of panic, but was later announced as false.
The man who sent that warning was fired by the Hawaii Emergency Management Agency, but says he is being treated unfairly and was sure it was a real drill at the time.
Days after the Hawaii warning, a Japan broadcaster mistakenly sent a text-message alert. It told Japan's residents that North Korea had launched a ballistic missile aimed there. After advising people to seek shelter, the warning was retracted minutes later.