Boston has spent Tuesday trying to come to terms with the aftermath of the bombings at the end of the city's marathon on Monday.
Three people were killed and more than 150 injured, 17 critically. One of those killed was eight-year-old Martin Richard.
Poignant images have emerged of tributes and meals left untouched as people fled near-by restaurants.
The full power of America's law enforcement agencies are investigating the explosions which the White House is treating as "an act of terror".
Emergency workers have been praised for their response saying lives had undoubtedly been saved.
More shamelessly was the spate of fake Facebook and Twitter accounts set up to capitalise on the tragedy.
Authorities have not given much away about any leads or suspects they may have, saying only it's likely to be the work of al Qaida or left-wing terrorists.