HOUSTON --A 21-year-old U.S. Marine from Tomball was killed in Afghanistan, the U.S. Department of Defense announced Wednesday. Cpl. Jeffery W. Johnson died Tuesday while supporting Operation Enduring Freedom in Helmand province. Another Texas Marine, 26-year-old Sgt. Kenneth B. May, Jr., of Kilgore, also died during the same incident. The details surrounding their deaths were not immediately released. Both of them were assigned to the 3rd Battalion, 1st Marine Regiment, 1st Marine Division, I Marine Expeditionary Force, Camp Pendleton, California.