We react with sorrow for the victims, in part out of fear for ourselves and for our loved ones. It could have been our father or our husband driving home from work. Then we get angry.
Nothing incites anger like a senseless, careless, unnecessary, manmade tragedy.
Death doesn't need any help. We already have to live with the awareness that death, with its limitless assortment of natural-born killers, lurks around every corner. Illness, disease, natural disaster or age will get us eventually. We shouldn't have to deal with death's irresponsible, reckless and, for whatever reason, disturbed human accomplices. So we get angry, enraged and outraged.