Boston Marathon bombing (59 images)

The NYPD shows a strong and increased presence in Times Square in New York City on April 15, 2013. Many American cities are on alert after two bombs exploded near the crowded finish line of the Boston Marathon killing two people and injuring more than 125 others. UPI/John Angelillo

Bomb dogs of the NYPD Explosive Detection K-9 Unit are on the job in Times Square in New York City on April 15, 2013. Many American cities are on alert after two bombs exploded near the crowded finish line of the Boston Marathon killing two people and injuring more than 125 others. UPI/John Angelillo

Newbury St. was closed off to pedestrians and motorists on Monday, April 15, 2013, after an explosion at the finish line of the Boston Marathon killed at least three people and injuring more than 100. Buerkle was a block away cheering on a friend's mother when the blast happened. UPI/Jacob Belcher

Pedestrians walk past a Metropolitan Tactical Police officer standing guard on the corner of Massachusetts and Commonwealth Ave on Monday April 15, 2013, after an explosion at the finish line of the Boston Marathon killed at least three people and injuring more than 100. UPI/Jacob Belcher