They are all paranoid now, but I don’t think they need to worry about the microwave, if it only beeps once. If it beeps twice, they need to head for the hills, cuz it’s gonna blow.
I have met a few microwaves that beep two or three times in a row when done.
But, yeah, generally it’s once.
However if you have PTSD from the incident, I’d think ANY beeping would set you off.