The inhumanity of man

I'll never be able to understand how a person can be cruel to the helpless little creatures.  My husband is a veterinary nurse and in his work he is witness to unimaginable evil.  Some days seem to be particularly full of horrifying  stories.  The worst of yesterday was a tiny kitten being tossed from a moving vehicle during morning traffic.  Thank god, a kind woman saw it happen and saved the little dear.  He still doesn't know if the kitten will survive, the skeletal damage is minimal, but the brain damage is difficult quantify and to heal.  

Is there a logical explanation for spurts of evil in the community?  The classic explanation of moon phase is illogical since we are at an intermediate waxing stage.  Could it be depression from our winter extending in to June this year?  Stress from the end of school, graduation, life changes.  I know it is ridiculous to attempt to make sense of something evil or of insane behavior.  This is a problem I've always had.  I remember as a small child asking my mother why John Lennon was murdered, she told me simply that the man was crazy, and you can't logically explain why.  This truth is as difficult to accept now as it was then.  It seems like every time I'm faced with a tragic event I try to justify it, rationalize why it happened, campus shootings, the suicide of a gifted young professor, harming helpless animals.  

It's pointless, but I can prevent myself doing it.