Statistically, the best thing I can do there is to keep him away from guns and to not have them in household. That really works, then he has only less fatal means available to him.
Then of course there are things like treating him as normal multidimensional human as opposed to as emotionless competing machine as people in these HN theads write about boys. Like, the boys I know in real life are way more multifaceted people, they do have emotions and everything. They have relationship issues with regards to their friends. They do have to deal with bullying from their friends both physical and emotional. When young, they are not walking constantly fighting trouble people in this discussion describe. When teenagers, they are not only-cares-about sport and violent games kind of guys. Nor closes himself to his room and ignores the family which is actually supposed to be cool thing about boys kind of guys.
Reading gender sterotypes on HN about boys, one would believe it is impossible for boy to become artist, writer, scientist or philosopher. Except in real world, boys and men engage in all those. But really, median boy that live in my bubble is not destructive machine. There are few boys that do cause disproportional trouble, but majority of them are nice humans.
Back to girls, I would be careful to trust people who find all these attempts to "not be serious" at the time of trying. Majority of them is serious. People who act like they are not serious or just cry for attention that needs to be ignored are how girls dont get help they need.