All humans are born wild, we don’t grow up or mature, we simply become domesticated and develop a larger vocabulary.
8 is old enough to know what is right and what is wrong, or at least, 8 is old enough to know what the adults say is right and what they say is wrong. (regardless of if the kid agrees or not)
Children are basically selfish, they have very pure clean logic, and are normally very frustrated because their small vocabulary wont allow them to express themselves.
My guess, is that the kid did this because of a lack of domestication or education.
Part of me wants to say that we should punish the kid, and the other part of me says we should tell him “don’t worry about those assholes, you was right to stab that other kid, it is the world that is wrong, not you, just try not to do it again”, and then punish all the adults for not having figured out how to make the world perfect yet.
At the age of 8, if I were the judge, I would be sentencing the kid to a stern talk, followed by 5 to 10 years of obligatory education, focusing mainly on the kids vocabulary and on giving him various moral and philosophy puzzles to examine and form opinions on.
While I am at it, I would send him off to see if he is a psycho or not, if not, no further action taken.