The world is full of violence, and the causes are many: wrong upbringing, mental illness, easily available weapons, poverty, alcohol and drugs, violence in movies and Halloween, wars and religious fanaticism, etc. To begin with, we need to teach children empathy!
My cousin's teenage daughter was at the mall, just arrived and walking through the doors when suddenly everyone came running at her screaming. She turned and ran out, found a shop nearby and called her mother, who thankfully managed to collect her before they shut the road. Traumatising. But oh I am grateful she was not 5 minutes earlier.
So very sad...............
Unfortunately this is not so uncommon in the US.
Katharine