I suspect the "loud noises" evidence was just the pretext used.
Almost certainly, a snitch, informant, or sting was how the authorities found the place.
LOL! Yeah, "Your taillight was out." "Well, it isn't out now." "It was intermittent."
It is absolutely amazing that media that report every silly high-tech futurist absurdity as if it were gospel apparently don't realize that a machinist can make a firearm. This has only been so for the last couple centuries, of course.