One warning sign that leaps out at me is that the suicidally depressed have often experienced deep trauma. The "psycho Vietnam vet" or "psycho Iraq war vet" has become a cliche in pop fiction.

But the kind of extreme trauma that can cause PTSD (whether it occurs in a war or in peacetime), if left untreated, is no joke. So many mass shooters seem to have been brutalized themselves in some way. So I'd be especially concerned if about someone who had been horribly scarred by physical or emotional abuse. It's a double tragedy, really, for the perpetrator as well as the victims.

Much appreciate your interest! If I see more in my notes that might interest you, I'll add it later.