Boston Marathon

Gallery: Rita Jeptoo, of Kenya, celebrates her win in the women's division of the 118th Boston Marathon Monday, April 21, 2014 in Boston.

Gallery: Tatyana McFadden, of the United States, gestures before breaking the tape to win the women's wheelchair division of the 118th Boston Marathon Monday, April 21, 2014 in Boston.

Gallery: Runners compete near the start in the women's division of the 118th Boston Marathon Monday, April 21, 2014 in Hopkinton, Mass. (AP Photo/Michael Dwyer)s

Gallery: Mike Poitras, of Dracut, Mass., wears the slogan "Boston Strong" on his head near the finish line before the start of 118th Boston Marathon Monday.

Gallery: Competitors in the wheelchair division of the 118th Boston Marathon leave the finish line Monday.

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

Gallery: Kevin Brown, of Brockton, Mass., gets an early seat near the finish line to watch the running of the 118th Boston Marathon Monday. Brown created the memorials to the 2013 bombing victims sitting near the the line, center rear.

Gallery: A Boston police officer and security dog pass by the photo bridge at the finish line for the 118th Boston Marathon Monday.

Gallery: Ernst Van Dyk, of South Africa, celebrates with his trophy after winning the men's wheelchair division of the 118th Boston Marathon Monday, April 21, 2014 in Boston.

Gallery: A runner toward the back of the fourth and last wave of competitors kneels to kiss the start line as he begins his running of the 118th Boston Marathon, Monday, April 21, 2014, in Hopkinton, Mass.

Gallery: Meb Keflezighi, of San Diego, Calif., crosses the finish line of the 118th Boston Marathon, Monday, April 21, 2014, in Boston.

Gallery: Rita Jeptoo, of Kenya, kisses the trophy after winning the women's division of the 118th Boston Marathon Monday, April 21, 2014 in Boston.

Gallery: Boston Mayor Martin Walsh places a wreath on Meb Keflezighi, of San Diego, Calif., after Keflezighi won the 118th Boston Marathon, Monday, April 21, 2014, in Boston.

Gallery: Meb Keflezighi, of San Diego, Calif., celebrates his victory in the 118th Boston Marathon Monday, April 21, 2014 in Boston.

Gallery: Meb Keflezighi, of San Diego, Calif., takes questions from the media during a news conference following his victory in the 118th Boston Marathon, Monday, April 21, 2014, in Boston.