Connotations of terms matter. Alleged is quite different from convicted. And by the way, we weren't talking about a person who allegedly shot a lot of people.....
I think it is likely that if the officer had not done what he did he would have been beaten to death or close to it, or murdered with his own weapon.
The responsibility for this is more on the parents than anybody else although kids are exposed to so much these days I don't know that they can be held totally responsible.