Been to Dallas lately?  I have.  There are mentally ill people wandering all over there.  Many have criminal records. This event could have easily happened there instead.  Or any big city.  But that doesn't fit your political narrative, does it?
And no, only until they are convicted of a 1st degree murder are they possibly going to be put to death in any state...except the one in your mind  This guy won't because he's clearly insane.
If there's blame to go around, I have to wonder about his mother, who called him a "nice person".  And his Facebook friends.  They knew what he was capable of.  Have you unfriended him yet Joe?