Dear me. All over a computer game? When did youngsters get so angry?
It'll be interesting to hear more about the shooter's background and possible causes for their behaviour.
There are very two distinct personalities, if we talk about gaming first.
The first person will loose and blame himself, he will say i made X and Y mistakes, and sure, while my team played bad, i could have played better, and perhaps there are some things i can do to improve it next time.
The second person will seek to blame others all of the time, and rage all of the time because all they want is an easy win, not a challenge.
This translates into real life too, people who blame others for their life, never taking responsibility, never seeking to improve themselves, never willing to put in the effort.
While most of these people are just scumbags, some of them eventually will snap.