2014 Boston Marathon

Meb Keflezighi of the United States celebrates after winning the 2014 Boston Marathon.

Meb Keflezighi of the United States reacts as he crosses the finish line.

Meb Keflezighi during the 2014 Boston Marathon.

Participants in the 118th Boston Marathon cool down at the finish.

Rita Jeptoo of Kenya kisses the trophy after winning the women's division of the 2014 Boston Marathon.

Boston mayor Marty Walsh places the laurel on the head of Meb Keflezighi.

Rita Jeptoo of Kenya celebrates after winning the women's division of the Boston Marathon.

Rita Jeptoo of Kenya reacts after winning the women's division of the 2014 Boston Marathon.

Rita Jeptoo of Kenya crosses the finish line to win the women's division of the 2014 Boston Marathon.

A general view of the finish line area on Boylston Street.

A man holds up a "Boston Strong" poster along the race course.

Apr 21, 2014; Boston, MA, USA; A young spectator holds a Boston Strong flag during the 2014 Boston Marathon. Mandatory Credit: David Butler II-USA TODAY Sports ORG XMIT: USATSI-179772 ORIG FILE ID: 20140421_jla_sv3_165.jpg

Monica Ross cheers after crossing the start line.

Race officials accompany Boston mayor Marty Walsh, former mayor Tom Menino , race grand marshal and former winner Bill Rogers at the finish line of the 2014 Boston Marathon on Boylston Street.

Scott Shupe cheers as he crosses the start line .

Jim Kalina waves to the crowd as he runs.

Elite runners including Ryan Hall and Meb Keflezighi.

A general view of the mass start during the Marathon.

Participants in the push rim wheelchair division at the start of the 2014 Boston Marathon.

Scott Porter at the start of the handcycle division during the 2014 Boston Marathon.

Tatyana McFadden after winning the women's wheelchair division of the 2014 Boston Marathon.

Tatyana McFadden finishes first in the women's wheelchair division.

Charlotte Flink looks to buy a Boston Strong flag from David Curry at the start line.

Cedric Schramm holds up a "Boston spirit" sign at the start of the Boston Marathon.

Elite runners Josphat Boit (left) and Meb Keflezighi (right) race during the 2014 Boston Marathon.

A makeshift Prudential Tower is erected by fans along the course.

A general view of the elite men's division start during the 2014 Boston Marathon.

Ernst van Dyk reacts after finishing first in the men's wheelchair division of the 2014 Boston Marathon.

Ernst van Dyk finishes first in the men's wheelchair division.

A young spectator holds up a sign during the 2014 Boston Marathon.

Andrew Lembcke (left) , Brandon Petrich (middle) and Bill Januszewski hang a Boston Strong banner before the start of the race.

Mike Herli of Marlboro, Mass. carries a Boston Strong flag before the start of the Marathon.

A flag hangs from the barricade on Boylston Street.

A Boston Strong flag and an American flag fly over Boylston Street.

Boston police officers who are part of the K-9 unit patrol Boylston Street near the Boston Marathon finish line.

Boston police officers from the K-9 unit patrol Boylston Street near the finish line.

Mobility-impaired runners gather at the start line for a moment of silence.

The 118th Boston Marathon gets underway as the mobility impaired runners leave the start line.

Pepi Bolognese cleans the finish line before the running of the 118th Boston Marathon.

Kevin Brown, of Brockton, Mass., gets an early seat near the finish line.

Race officials wire the electronics for the start line.

Two runners walk with garbage bags on to keep them warm prior to running the Boston Marathon.

Runners cue to board buses.

Andrea Prusinski, left, hugs friend and Boston Marathon runner Karen Schroeder, of Denver, before boarding the bus to the starting line.

Anthony Bisenti cleans the finish line before the running of the 118th Boston Marathon.

A runner huddles under a blanket while getting ready to run the Boston Marathon in the Boston Commons.

A runner with a temporary Boston Marathon tattoo gets ready to run the 118th Boston Marathon in the Boston Commons.

A runner tucks gel packets into his socks while getting ready to run the Boston Marathon in the Boston Commons.

Runners get ready to run the Boston Marathon in the Boston Commons.

A couple huddles while waiting to load a bus to take them to the start of the Boston Marathon.

Quincy, Mass., police stand near the starting line of the 118th Boston Marathon.

Runners eat a last meal before loading a bus to take them to the start.