Playing Devil's advocate here, in the frames shown it would be necessary for the driver to use his left hand to shoot, as using his right hand would have required his arm to be fully extended. But the frames here show that the shot was fired over his right shoulder, so it had to be his left hand that held the pistol. So was Greer left-handed...or right-handed? Of course if he had practiced that shooting technique a lot, even if he were right-handed, he might have pulled it off.