The police block off a street near the place where explosions happened in Boston, the United States, April 15, 2013. Three people were killed and 144 people wounded in the explosions according to the statistics published on April 16. (Xinhua/Wang Lei)

A policeman is on duty near the place where explosions happened in Boston, the United States, April 15, 2013. Three people were killed and 144 people wounded in the explosions according to the statistics published on April 16. (Xinhua/Wang Lei)

 

Two policemen guard the Brigham and Women's Hospital where the injured people were treated after explosions happened in Boston, the United States, April 15, 2013. Three people were killed and 144 people wounded in the explosions according to the statistics published on April 16. (Xinhua/Wang Lei)