The gun registration screen says that the business partner owns a "Baretta" model handgun. The correct spelling of the name is "Beretta".
The low rumble extracted from the 911 call would not have been passed over in the phone system. The bandwidth of voice transfer in standard telephony is limited roughly between 300 and 3000 Hertz. This carries over the frequency range needed for intelligible speech, but saves bandwidth when transferring multiple calls over a digital network.
In the show, a phone call was spoofed from a large office building to a private line in another area of the town, so as to appear that the call originated at the private home. This was done by a pair of wires and a lineman's phone in the junction box near the home. However, while phone lines in a residential area could be routed through small boxes over dedicated analogue trunks, it is more likely that the office building had all its telephony transmitted over a few digital copper trunks or a fiber-optic trunk. Although the telephony from the residences would eventually be also collected in such way, it takes more than just a pair of wires at a remote box to do such a spoof. More like contracting the phone company to assign the private number to the line in the office - this would leave a paper trail and probably take a few days to process either way - so it would not be handy for a temporary and quick setup. They could have done that spoof between two lines that physically went through that same box as analogue trunks.