Motive, schmotive. Loughner is crazy. Probably paranoid schizophrenia, which often develops in early adulthood. Fio knows. One of her nephews is paranoid schizophrenic. She's written about him before. He's the one to whom cats and mailboxes talk, to whom radios and TVs broadcast warnings that the police are after him, whose knees the Ku Klux Klan has damaged by sending electronic rays through the wall of his ratty apartment because he talked to a Black person.
He's the one who tried to kill his mother.
But he's still running around loose, on his own, and he doesn't take any medication. After all, this is a democracy, and he's entitled to make his own decisions regarding medical treatment. Except that's exactly what his affliction prevents him from doing, making his own decisions--at least rational ones. It's like requiring a blind person to see.
Like expecting Jared Loughner to realize the inhumanity of his actions.