New Hampshire authorities said yesterday that they will not press charges against a former Marine who stepped into a deadly shooting and killed a 24-year-old high school dropout who had moments earlier fatally shot a police officer. The former Marine, Gregory W. Floyd, 49, was driving with his son along Route 116 in Franconia on Friday night when he saw Liko Kenney, 24, shoot Franconia Police Corporal Bruce McKay, 48, four times in the torso. After Kenney drove his Toyota Celica over McKay as the officer lay on the ground, Floyd grabbed the officer's service weapon and shot and killed...