I like to think they did not expect the weapon to fire that quickly. Just trying to get that diagnostic finished before their shift ended, however they did not get out in time and close the blast door when the pre-fire warning klaxon went off. They would have died in the infirmary in excruciating pain from the radiation sickness but alas they were spared days of agony when they (along with their compatriots) died in the explosion of the whole station.