Cathy Garner was worried that her son Nick Alden would be in danger in Afghanistan. Alden, a U.S. Air Force airman, didn’t make it to Afghanistan. He died Wednesday when a gunman whom authorities are describing as an Islamic extremist began shooting on a bus at an airport at Frankfurt, Germany. Alden was 24. Garner got the news in a telephone call from her ex-husband, who told her that their youngest son charged the gunman after seeing him fatally shoot the bus driver. At least 10 airmen dressed in civilian clothes were on the bus at the time of the...