Cameras rolled as suspect Jared Loughner allegedly fired all 31 bullets in the clip of his Glock, plus another round that was already in the chamber, at a supermarket in Tucson, Ariz., on Jan. 8. At the outset of the melee, unidentified sources who have seen the video tell the Washington Post, Loughner walked straight up to congresswoman Gabrielle Giffords and shot her above the left eye from about two or three feet away. Within moments, Loughner also allegedly shot Chief Arizona U.S. District Judge John Roll, who had tried to take cover under a table. As Roll did so,...