While lots of people would probably say that the murderer was psychotic, that's too easy. He might have been literally demon-infested, or he might have been just a blackheart looking for an excuse. In any case, even one's own heart is mysterious to oneself; and our present state of general knowledge is most unclear about how the spiritual and the psychological interrelate. Speculation thereon doesn't address the most important question: would we rather curse or bless?
Can anybody doubt that the forgiving attitude being shown by the families and town of the recent mass-murder victims is better, and will bear richer fruits, then cursing the murderer? I've heard it remarked that it's too bad he killed himself to climax the bloodbath, because that deprived society of two important possibilities: either kill him ourselves (judicially of course), or send him to prison for life, where he would certainly have been sodomized for a long time before dying or being killed himself. And I'm sure plenty of others wish that, in any event, he's roasting forever in hell, since what we would have done to him if given the chance would have been too good for him. It's understandable that many people deal with their emotions in that sort of way. But it only makes things worse.
The paramount task, of which the grief process is a needed part, is always spiritual healing. Indulging negativity does not aid that process. The Amish are showing us what really needs to be done. If we took the lesson, perhaps the Church's wisdom about capital punishment would be more widely heeded.