HAWTHORNE — Tears were shed Tuesday in this town of 3,000 for seven unknown U.S. Marines. “We are all military today,” said John W. Stroud, junior vice commander of the Veterans of Foreign Wars in Hawthorne. “They are our brothers in arms.” “They died in my hometown,” added Myra Sterling. “It feels like we somehow are responsible. They didn’t die in combat, but they died in service to our country.” About 600 residents turned out for a memorial service in Veterans Park to honor the Marines who died just after 10 p.m. Monday at “Old Bomb,” a training area about …