20-year-old male is the perfect candidate for the schizophrenic diagnosis (or to be used as an assassin for the same reason).
If it’s ever found that the US government is using these “gunmen” as assassins in order to advance a political agenda... I can’t even say what fate I hope awaits whoever is responsible.
Anyone capable of targeting innocent children has most likely been utilized by someone seeking political gain. It would surprise me if this was not a political job and about the only other cause would be an islamist killer.
I totally believe that's one of the primary sources of these mass shootings. Can't prove it, but there's a pattern emerging that can't be ignored.