This would be my solution as well. Caring for each other is a very strong but passive way of reminding people that they are part of the group, that they are wanted, needed, and worthy of health and happiness (mental health). I think it would go a long way to countering the alienation and isolation that I believe is the primary driver for these shooters. Sure, they get radicalized online, or in radical spaces, but what drove them to seek those spaces or forums in the first place? The feeling that they didn’t belong. If you feel like you belong you see others as extensions of yourself, and the idea of gunning down a bunch of yourself becomes less palatable.