Monday's deadly attack on the Boston Marathon has penetrated the consciousness of Americans in different ways. The target was not a symbol of power or dominance, but a crowd of people at play, a strike at "the heart of America" that makes many feel insecure. Does giving in to such fear mean that "terrorists" win? Do we really know this was a "terrorist act?" What can Americans learn from other countries? President Obama rallied Boston at an emotional memorial service today, mourning the dead and cheering the wounded. He said Boston represents the best of American values, as exemplified by support for runners along the way and help for the victims when "celebration turned into tragedy." He vowed again that the perpetrators will be found and brought to justice, but officials still haven't discovered who they are or why they committed such atrocious crimes. We hear from his address and get a variety of opinions amid a cloud of uncertainty.