i think that is part of the logic of these people.. .. they are self centered to the extreme and think themselves as victims and think they are all alone and anyone else wants them harm
so partially because of this.. and partially because he wanted to "get back at society" it doesent matter who he kills.. because he thinks that everyone in a way has wronged them... and whoever he kills, is just another victim of said soceity they "cant help" but kill those people because they are no the ones responsible its everyone else that "made them do it" so in their logic they are not really killing them its everyone else that drove them to do it
although its the most common to happen at a school because there they can kill the ones who bullied them, rejected them or just.. because they are the same age they are the most alike to the killer only they resemble things they lack.. be that in academical archievement.. social status. appearance and so forth
and makingmusic i hope you were joking about german gun controls laws :P
