Two bombs rocked Boylston Street in Boston during the Boston Marathon.  Two more undetonated devices were also found.  And now the investigation begins.

Federal, Massachusetts and Boston officials did not have any prior warnings or threats of an attack on the race.  Authorities spent an hour or two sweeping the entire marathon route and Copley Square.

FBI and Homeland Security officials have begun their investigation, interviewing people of interest, and even searching an apartment in Revere, MA.