DEVELOPING: The FBI will release key video from the Boston Marathon bombing at a 5 p.m. news conference in Boston, Fox News has learned. The video, believed to be of the crowd around the finish line of Monday's race where two bombs exploded, killing three and injuring 176, could provide clues or even show the culprit. Earlier, Department of Homeland Security Secretary Janet Napolitano said investigators were seeking individuals seen in footage or photos. Napolitano stopped short of calling the individuals suspects or describing them or their demeanor in her remarks, made to the House Homeland Security Committee on Thursday. Napolitano...