Boy, 8, among the dead in Boston Marathon Explosions

BOSTON, MA (ABCNews.com) — An 8-year-old boy was one of two casualties when bombs tore into the Boston Marathon today, a law enforcement source told ABC News.

At least 115 people were injured, including several children with severe trauma, when bombs exploded almost simultaneously at the crowded Boston Marathon on a day that was supposed to be one of celebration.

Within hours of the explosions, law enforcement officials, including those with the Bureau of Alcohol, Tobacco, and Firearms, were questioning a potential person of interest at Brigham and Women's Hospital, where many of the injured were taken, sources told ABC News. Officials cautioned that it was too soon to say whether the person was an important witness or a person of interest.

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Photo Courtesy: Associated Press