I did this the other day. I was re-wiring an overhead light into a ceiling fan, and I got a cell phone call and got off the ladder and took the call. Walked back into the room after the call and it was darker (the sun moved) and I flipped the switch sending a shower of sparks in the room. oppsss. I am not what you call a dumb, just forgot and was thinking of something else.
Yeah I get it. Long ago I was working on a DIY project with my dad and we pulled the wrong circuit breaker. He went to cut through the main wire to 12 overhead lights and the "spark" burned a hole in the wire cutters and caused quite the curse from my father, who luckily only got a mild burn and a mild shock. It did cut a perfect circle in the blades of the cutter. So anyone can make a mistake.
I suspect that you, like myself and my dad, weren't standing in a room full of fuel fumes so thick that we couldn't breath. If we were I suspect, hell I'm certain, you or we would have ventilated the room and found the source of the fumes before doing anything electrical.
Also for the record. The event that triggered the infected happened a few months ago. Although they are inspected annually commercial sprinkler systems are designed and built to go years without any kind of maintenance. They fail inspection if there is any indication that that standard has been compromised. These systems are built to function without power or city water. So while the authors give lip service to something must have gone wrong maybe not enough water pressure. These are 5 sigma systems inspected on a regular basis and a complete failure is about as likely as getting struck by lightening.
It's lazy writing. But it's only a single occurrence in an otherwise well written and well plotted game/story. If the rest of the story wasn't so well written this wouldn't rate a mention. It's only notable because it falls so far below the standard that they've established.