Certain cultures?
Actually the behaviors of mental illness cut across cultures and races. They may express differently ie in English speaking areas a delusional person may think he or she is the Queen of England. In other areas the delusional content may focus around being a ghost.
Christians visiting the Holy Land will sometimes have a psychotic break and think they are the Christ... I can go on.
It sounds lik you’re assuming th 15 yr.. old is mentally ill. If or not certain cultures are more violent than others. That’s a fact.
We don’t really know what it is. We only see a tiny part.
We DO know that “mental illness” is over-diagnosed, and seems to crop up as an excuse for everything, including conservatives trying to divert from “guns” by screaming “mental illness” at every mass murder. (Which is more likely with MASS murder, but still in this permissive self-centered day and age, not necessarily the reason.)
Given this boy’s background of welfare-Queen single black mom, I’m just as inclined to stick to “the culture” as the reason.