Commentary SHANKSVILLE, Pennsylvania—The first thing you notice about Frank Siller is the resolve in his mission. Each step he takes along Shanksville Road on the outskirts of this Somerset County town is done with purpose. The sound the steps make is a forward motion; there is no hint of retreat. You can imagine it is a trait he shared with his brother Stephen who, 20 years ago in his capacity as New York City firefighter, went running toward the burning World Trade Center twin towers in the early moments following the deadly terrorist attacks on Sept. 11, 2001. Siller is walking toward the national park that honors the Flight 93 passengers who made the conscious decision that beautiful, cloudless day to do whatever it took to save others who were in harm’s way. It was a decision that sacrificed their own lives to save others, Siller said. “Those were the …