It doesn't sound like violent girl gangs are a big problem in this particular community. This is another nutty loner with a rifle. Instead of going up in a bell tower somewhere to pick people off he just fired out his bedroom window.
That doesn't mean we need to suspend the 2nd Amendment or the right to self-defense. But this guy went way out of bounds by any reasonable standard.
Unfortunately, the scenario I've described above isn't just what these girls did, but the MO of at least two home-invasion teams.
Also, note that these idiot girls were shot at when they FIRST TRESPASSED, and they came *BACK*.