Whatever the kid's background, temperament or personality,
he stabbed someone!!! If nothing is seen to be done about it, then it will be seen as condoning the incident.
Somebody is answerable for this act of violence, it simply shouldn't have happened. It is not normal nor
acceptable for children to commit acts of violence like this. i.e. there is something very wrong with this picture.
The scary thing is that this is not an isolated incident. I have been hearing of more + more cases of children assaulting + even being responsible for deaths

Even today on the radio news there was one where children were heard chanting "kill him, kill him". What the hell is going on here?!
This expression of outrage is not directed at you Liam

it's just expressing shock on this topic. We (society, adults etc.) cannot allow this behaviour in children to continue or escalate, or we are in serious trouble as a society