Why did the Finland mass murderer, show sadism in his text and videos prior to the killings?

Answer 1

Perhaps because the little bast**d was NUTS! Or mommy yelled at him.Or a girl laughed at him.Or the voices in his head said it was okay.
Who the hell knows or cares?

Answer 2

As the killer said in the video, he tried to bring out the issue in a deeper sence. His intention was beyond merely mass-acre.

Perhaps, he tried to alert politicans on their education profile.

You can see the T-shirt. It said: humanity is overrated. Obviously, he thought education is too much in humanity and even distorted the humanity. Teachers are forced to be too kinds and syllabus are to naive.

As reported, the killer has been tortured by other students. Perhaps, he brought that issue to teachers and his headmastress. Their answer would be "forgive". Forgive those attacked him. This was a biblical teaching in the surmon in the mount. When someone hit your left, let them hit your right also. However, for ordinary people, he would demand justice. Then, he exercised his right in self-defence and massacre those who have tortured him and also kill those teachers who are too kind to those kids.