By Max Bearak, The Washington Post For many of us, the images of 5-year-old Omran Daqneesh, injured, ashen and bewildered after an airstrike in Aleppo last month, crystallized the horror of Syria’s civil war. It made us wonder, again, how that horror might be stopped. For Alex, a 6-year-old from Scarsdale, N.Y., it called upon an even deeper sense of responsibility and shared humanity. In a letter to President Barack Obama, Alex wrote: “Remember the boy who was picked up by the ambulance in Syria?