WSJ | In Arizona, public mental-health services are among the worst in the nation. In a 2008 survey by the Treatment Advocacy Center, Arizona ranked next to last among all states in the number of psychiatric hospital beds per capita. If you don't have hospital beds and outpatient clinics to treat mentally ill people, those people don't get treated. Thus the tragedy was somewhat more likely to happen in Arizona because mentally ill individuals are less likely to receive treatment there. Although Arizona is the worst state, except for Nevada, in psychiatric-bed availability, there is no state that currently has enough beds for its mentally ill population, according to the Treatment Advocacy Center study. This tragedy occurred in Arizona, but it could easily have happened in any state.

Mr. Loughner's delusions fixated on Arizona Congresswoman Gabrielle Giffords, one of 12 seriously injured in the shooting. Some have speculated on the possible relationship of our acrimonious political climate to the incident. It is, however, unlikely that there is any such relationship, since similar tragedies occur in politically harmonious times as well.
The motivation for such killings is usually based on psychotic thinking, not political thinking. Dennis Sweeney killed Allard Lowenstein because he believed that Lowenstein had implanted a transmitter in his teeth that was sending messages to him. Russell Weston stormed the Capitol because he believed the government had hidden a machine there that could reverse time.