Murder and Heros in Tucson

Trouble in Tucson
I don't believe in violence of any kind. Therefore this tragedy in Tucson troubled me. What caused it?

Was it words?
Many "talking heads and the Pima County Sheriff said it was the vitriol. So I looked up vitriol and this is what was shown:

vit·ri·ol/ˈvitrēəl/Noun

1. Sulfuric acid.

2. Cruel and bitter criticism
An article in the New York Times was titled

"Bloodshed Puts New Focus on Vitriol in Politics"

and explained how inflammatory languages, threats, and implicit instigation cause hatred.

Additional topics could include:
Was it race?
Was it craziness?
Was it preventable?
Was it something I did or didn't do?