Maratona e Bostonit

Runners in the first wave of 9,000 cross the start line of the 118th Boston Marathon, in Hopkinton, Mass., April 21, 2014.

A State Police Special Response team patrols past posters of encouragement at Wellesley College before the start of the 118th Boston Marathon, Wellesley, Mass., April 21, 2014.

Workers move security gates into position in front of Wellesley College in the early morning before the start of the 118th Boston Marathon, in Wellesley, Mass., April 21, 2014.

Participants in the wheelchair division of the 118th Boston Marathon start their race, in Hopkinton, Mass., April 21, 2014.

The second wave of runners make their way down Main Street during the 118th running of the Boston Marathon in Hopkinton, Mass., April 21, 2014.

Boston police officers, part of the K-9 unit, patrol Boylston Street near the finish line before the start of the 2014 Boston Marathon, Boston, Mass., April 21, 2014.

Till T. Teuber of Hamburg, Germany, prepares himself before the 118th Boston Marathon, in Boston, Mass, April 21, 2014.

Elite men runners leave the start line in the 118th running of the Boston Marathon, in Hopkinton, Mass., April 21, 2014.

Andrew Lembcke (left), Brandon Petrich (middle) and Bill Januszewski hang a Boston Strong banner before the start of the 2014 Boston Marathon, Boston, April 21, 2014. (Greg M. Cooper-USA TODAY)