The Latest: FBI leads 'potential terrorist investigation' in Boston

An unidentified Boston Marathon runner leaves the course crying near Copley Square following an explosion in Boston Monday, April 15, 2013. (Credit: AP Photo/Winslow Townson). Updated Tuesday, April 16, 9:20 a.m.An unidentified Boston Marathon runner leaves the course crying near Copley Square following an explosion in Boston Monday, April 15, 2013. (Credit: AP Photo/Winslow Townson). Updated Tuesday, April 16, 9:20 a.m.MSNBC.com. Create sub-clip. Sen. Susan Collins on Saturday became the first Republican to publicly say she will vote in favor of tighter gun legislation, but sponsors of the bill that expands background checks still worry theFile Photo: Former President George W. Bush speaks at the Economic Club of Southwestern Michigan May 28, 2009 in Benton Harbor, Michigan. Bush was to discuss his presidency and life, as well as the economy and worldFile Photo: Former President George

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