It could have been worse.
Gabrielle Giffords was shot in the face, she was targeted deliberately, and obviously identified and singled out by her assailant. And six other people at her rally were killed.
People do need to chill out. Even from a purely tactical point of view, political assassination does not work. It only makes a martyr of the victim, and gives his supporters an excuse to launch a campaign of vindictiveness and revenge.