After seeing that the young shooters didn't just snap, the researchers believe that more responsibility for the shootings rests with adults. If you view these shooters as on a path toward violence, it puts the burden on adults. Believing that kids snap is comforting. Although there is no profile, the shooters do share one characteristic. When they have additional pain, additional grievances, they are less likely to reach out and talk to someone, less likely to be listened to.
Violence is the only way they start to feel they can get a result.