Off topic, but you really think there arnt automatic turrets, seems very feasible today, especially in a situation like a sewer where you really dont have to worry about shooting the wrong (moving) thing.

Not quite there, but this thing is successful. It’s a self resetting trap, with its kill attracting more target species. Refilling if after ~25 kills is more expensive that resetting a manual trap, but the labour cost is ~25x cheaper. https://goodnature.co.nz