Wifi jammers have a fairly short range, especially the type you can carry around in your pocket. They won't knock out an entire neighborhood. They might not even knock out an entire home system, just the parts nearest the jammer. Think 50-100 feet or so, depending on model and power. That part could be important in this case.
They are also illegal for anyone to own, sell, or operate under federal law. Since they work by flooding the typical wifi bands of 2.4GHz/5GHz with noise, they can also be detected as they leave an unmistakable signature.
Think of it like a digital hurricane. Nothing else can be heard over it.
This is why EVERY home security system needs to include a hard wired ethernet component to complement wireless. Criminals are increasingly using jammers, which unfortunately aren't that hard to find if you are truly determined, regardless of the fact that they are strictly illegal.
A camera that is hardwired to the router and goes through a cable is unaffected by any jammer, and will record to the cloud, send notifications to your phone, and continue to operate normally even in the case of a jammer attack. Some even detect jammer attacks (because of a sudden flood of information on 2.4 or 5 GHz bands which can ONLY be a jammer).
Everyone should know this for their own security. ANY wireless camera is pretty easy to take offline by these criminals.
Now, if only the one camera on the neighbor's house closest to NG's house was affected that is solid evidence of a portable jammer. It could also explain why cameras reportedly went offline yet captured images later on.
As the perp walked around the house the radius of the jammer would move as well, causing its effects to travel. It would also suggest where the perp was and when, as most systems will tell you in the event log when exactly they went offline.
Moral of this story: install hard wired cameras. They are harder to install but jammer proof.
All of this means this is more likely to be a lone perp. Walkie talkie suggests a second person. Wifi jammer doesn't move the needle either way, but it doesn't support a second person the way coms would.