Hopkinton

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Mobility-impared runners David Abel, left, Juli Windsor, and Scott Rigsby compete in the 118th Boston Marathon Monday, April 21, 2014 in Hopkinton, Mass. (AP Photo/Michael Dwyer)

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Mobility-impaired runners gather at the start line for a moment of silence before the 118th Boston Marathon Monday, April 21, 2014 in Hopkinton, Mass. (AP Photo/Stephan Savoia)

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Mobility-impared runners David Abel, left, Juli Windsor, and Scott Rigsby compete in the 118th Boston Marathon Monday, April 21, 2014 in Hopkinton, Mass. (AP Photo/Michael Dwyer)

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Father and son Boston Marathon race team Dick Hoyt, right, and his son Rick Hoyt walk across the start line as they warm up before they run the 118th Boston Marathon Monday, April 21, 2014 in Hopkinton, Mass. (AP Photo/Stephan Savoia)

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Mobility-impaired runners gather at the start line for a moment of silence before the 118th Boston Marathon Monday, April 21, 2014 in Hopkinton, Mass. (AP Photo/Stephan Savoia)

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Quincy, Mass., police stand near the starting line of the 118th Boston Marathon Monday, April 21, 2014 in Hopkinton, Mass. (AP Photo/Michael Dwyer)

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A military policeman stands near the start line of the 118th Boston Marathon Monday, April 21, 2014 in Hopkinton, Mass. (AP Photo/Michael Dwyer)

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Buses carrying runners arrive at sunrise in Hopkinton, Mass., for the start of the 118th Boston Marathon Monday, April 21, 2014. (AP Photo/Michael Dwyer)