But XV has continued the pattern first observed when he was little, and is gradually esculating with larger weapons and more vulnerable targets.
'Tis a shame. Unlikely anything positive will come of this. I've seen similar situations before.
Child has a sociopathic personality. Most -- though certainly not all -- violent sociopaths are created due to a combination of neglect and abuse. Some, however, have parents who give them everything they want, and either deny or ignore any evidence that something may be "wrong" with their child . . . in their eyes, he can do no wrong. Therefore, counselling and medication are non-options.
'Tis a frightening thing to look into the eyes of a child and see no light there . . . naught but a festering blackness. Such a one seeks to harm others for the "joy" of overpowering those who are weaker. It will get worse. Some monsters are not created by systematic abuse . . . a rare few seem to be born evil. An unpopular theory when speaking of children.
The father of A,B,C should forbid his children to associate with XV, and write a log of all past and future incidents -- including dates, times, witnesses, and statements from others. The situation with the teacher sounds odd . . . if this is a public school in the U.S., complaints can be filed that go above the principal and superintendant, if need be. 'Tis a shame that the community has united against the father in support of XV . . . why do you think this is? Is it something more than, "Oh, he's only a child, and we all know that a bully would never
intentionally injure another child" . . . there are thousands of documented cases of young children maiming and killing other children . . . "Oh, but a
child doesn't understand the consequences of his actions" . . . maybe not fully, but the intent to harm is certainly there, and without responsible adult supervision XV is free to take this as far as he wants.
If the majority of the community is hostile to the father, he should seriously consider moving. Otherwise, if little XV were to run away or be the victim of a hit & run, you'd have a dozen neighbors telling the authorities, "Yeah, that paranoid guy
hated llittle XV."
Bad situation all around. Sometimes it really is for the best to admit it's a "no-win situation" and leave . . . even if you know you're right.