If you refer to statistics, and there is official international statistics on that matter, please provide reference. So far I never see any evidence for your point of view. You refer to it like commonly "known" fact, but it is not.
It should also be noted that the data set they used only include mass killing with guns, and not mass stabbings. Those also happens, including here in Sweden a year ago at a school. But if you don't like that data then bring more and we can discuss.
Two things pops out. First that the variance is massive within the united states. The second part is that 63 percent were suicides. It is very doubtful that a single correlating factor accounts for the variance.
Situation is far more complex than you presented. He probably fall under that category under federal law.
Check carefully https://en.m.wikipedia.org/wiki/Ages_of_consent_in_the_Unite...
Anyway, it is up to court to make legal decision on that matter. BTW, even ONE case with that 14 old teen if proven to be true would be sufficient and give him long term to serve in prison. Well, you probably also expect better moral standards from judge, isn't it?