From Reuters:
A law enforcement vehicle carries a bomb disposal device through Watertown during a search for the two men suspected of setting off two explosions during the Boston Marathon in Watertown, Massachusetts, April 19, 2013. Massachusetts State Police warned people in the Boston suburb of Watertown not to open their doors and said they would conduct a door-to-door, street-by-street search due to what it called a fluid situation.
REUTERS/Lucas Jackson