He killed a little girl, even most criminals draw the line at killing children. He's so obviously insane it seems impossible that it wasn't noticed sooner.
Right after it happened everyone thought it was political and because of harsh rhetoric on both sides. But what they SHOULD have been talking about is how nobody noticed and the very sad stigma surrounding mental health in this country.
From what I heard it was noticed sooner many times. One of the major discussions regarding this shooting was how could something similar be prevented next time since there were so many warning signs, complaints, and plain bizarre behavior on record.