Seven Marines with 1st Battalion, 9th Marine Regiment, 2nd Marine Division, II Marine Expeditionary Force, were killed and eight others were injured, which includes a Navy Corpsman, in an explosion during a live-fire training exercise at Hawthorne Army Depot shortly before 10 p.m. Monday. ■ PFC Joshua M. Martino, 19, of Clearfield, Pa., served as a mortarman assigned to 1st Battalion, 9th Marine Regiment. He joined the Marine Corps in July 2012. Martino’s awards include the National Defense Service Medal and Global War on Terrorism Service Medal. ■ Lance Cpl. David P. Fenn II, 20, of Polk City, Fla., was …