10 BEST PHOTOS: Unbridled spirit on show at Boston Marathon

A father carries his son on his shoulders as he waits for the commencement of the race at the starting line of the 118th Boston Marathon in Hopkington, Massachusetts on Monday.

Meb Keflezighi became the first US male athlete to win the Boston Marathon in three decades on Monday, the first running of the race since last year's fatal bombing attack.

Runners wait for the start gun at the starting line of the Boston Marathon in Hopkington, Massachusetts on Monday.

 Keflezighi said memories of the victims of last year's bomb attack carried him through the last, difficult miles of this year's Boston Marathon.

Two police officers look on from a rooftop near the start area of the 118th Boston Marathon in Hopkinton, Massachusetts on Monday.

Security presence has been increased this year, due to two bombs that were detonated at the finish line last year, killing three people and injuring more than 260 others.

Runners get ready to run the Boston Marathon in the Boston Commons in Boston, Massachusetts on Monday.

The Elite Women's division participates in the 118th Boston Marathon in Hopkinton, Massachusetts on Monday.

Tatyana McFadden celebrates as she wins the women's wheelchair division of the Boston Marathon in Boston, Massachusetts on Monday.

Shalane Flanagan of the United States receives medical attention after crossing the finish line at the 118th Boston Marathon in Boston, Massachusetts on Monday. 

Kenya’s Rita Jeptoo hugs a fan after winning in the women's division of the Boston Marathon in Boston, Massachusetts on Monday. 

Runners make their way down Boylston Street to receive their medals after competing in the Boston Marathon in Boston, Massachusetts on Monday. 

Meb Keflezighi of the United States celebrates with the trophy after winning the 118th Boston Marathon in Boston, Massachusetts on Monday.