There is N E V E R a reason to harm children. Quoting: Anonymous Coward 18012248
This is beyond mental illness. This is just evil.
I go with mental illness - contrived by home environment I'm sure, but it still resulting in mental illness. I see it daily at my school, and we have a problem in our society.
Kids grow up in households where there is a lot of turbulence (divorce, many "daddies" in and out of the home - some abusive). The parents are dysfunctional, but they always have the "don't you dare do that to my kid" attitude - because they believe the kid is basically good but has had to put up with a lot and people just need to let him alone rather than try to correct him. The kids aren't made to take responsibility for their actions because the parents always take their side and make excuses, which in turn stunts their emotional development of the child.
The schools let the kids run wild and rule the roost as well, because those same parents are constantly threatening lawsuits - especially if they can make the case that the child is special needs. If a child is special needs, it's nearly impossible to expel him.
Then, those same kids are plopped down in front of violent video games all night because the parents don't want to deal with a difficult child. These kids don't really get that other people are real and have feelings because they've been made into narcissistic brats, often mean towards others while at the same time shunned by the normal kids because of their brattiness (and their parents are always boo hooing that their kids are being bullied).
So, the shooter "hates" his mom (who like many of the above parents finally realized too late she has to put her foot down) and he goes off blows her away and takes a bunch of kids with her - just like he's playing a video game - they mean nothing-nobody means anything but his own needs, sick as they might be.
Let me tell you - if you work around troubled kids long enough, you can pick them out of a classroom of 25 in 4 or 5 minutes. I guarantee this young shooter has a long history.