Missing some information
"However, it is also possible that this version of events is also untrue, and the warning officer simply screwed up first by choosing the wrong option, and then refused to pause when given the warning prompt. He or she could simply be protecting their job and reputation."
According to the BBC report, the warning officer has been a "source of concern" to colleagues for years, and has confused drills with real alerts multiple times in the past. He's also been fired. It's possible everyone else is conspiring to use him as a scapegoat, but it's fairly unlikely that he's trying to protect his own job or reputation, given that he no longer possesses either. Given that two of the people in charge have also resigned, such a conspiracy also seems unlikely; it really was just a massive screw-up all round.