-support
You underestimate how loud suppressed weapons are, especially indoors. They can still very much be heard, since the vast majority of firearms fire supersonic ammunition.
If you want to make the argument that it's video game logic and that the guns are actually quiet, there's still the fact that 939 can hear and echolocate extremely effectively, having no eyes. Its sense of hearing would far outstrip a human's capabilities and would be able to hear the suppressed gunfire clear as day.