A commuter injured by the blast at the Park Kultury subway station shortly after Monday's explosion. Egor Barbatunov/AP hide caption

itoggle caption Egor Barbatunov/AP

Obama holds 4-year-old Barack Anthony Stroud at the University of Iowa Field House in Iowa City, Iowa, Thursday. Saul Loeb/AFP/Getty Images hide caption

itoggle caption Saul Loeb/AFP/Getty Images