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Open Image ModalIn this photo provided by The Daily Free Press and Kenshin Okubo, people react to an explosion at the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Daily Free Press, Kenshin Okubo) MANDATORY CREDIT (credit:AP)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(02 of41)
Open Image ModalBOSTON, MA - APRIL 15: Two blood stained feet of a man hang outside an ambulance outside a medical tent located near the finish of the 117th Boston Marathon after two bombs exploded on the marathon route on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(03 of41)
Open Image ModalBOSTON, MA - APRIL 15: The bandaged leg of a man hangs outside an ambulance outside a medical tent located ear the finish of the 117th Boston Marathon after two bombs exploded on the marathon route on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images) (credit:Getty Images)
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Open Image ModalThis photo provided by Bruce Mendelsohn shows the scene after two explosions occurred during the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/ Bruce Mendelsohn) MANDATORY CREDIT (credit:AP)
Barack Obama(05 of41)
Open Image ModalPresident Barack Obama speaks in the James Brady Press Briefing Room at the White House in Washington, Monday, April 15, 2013, following the explosions at the Boston Marathon. (AP Photo/Charles Dharapak) (credit:AP)
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Open Image ModalMedical workers aid an injured man at the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two bombs exploded near the finish of the Boston Marathon on Monday, killing at least two people, injuring at least 22 others and sending authorities rushing to aid wounded spectators. (AP Photo/The Boston Globe, David L. Ryan) MANDATORY CREDIT (credit:AP)
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Open Image ModalPeople react to an explosion at the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Boston Globe, John Tlumacki) (credit:AP)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(08 of41)
Open Image ModalBOSTON, MA - APRIL 15: A woman, with blood on fingers, is loaded into an ambulance after being injured after two bombs exploded on the marathon route on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(09 of41)
Open Image ModalBOSTON, MA - APRIL 15: A woman is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(10 of41)
Open Image ModalBOSTON, MA - APRIL 15: A woman looks at the blood on her hands as she is loaded into an ambulance after being injured after two bombs exploded on the marathon route on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(11 of41)
Open Image ModalBOSTON, MA - APRIL 15: Runners react near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(12 of41)
Open Image ModalBOSTON, MA - APRIL 15: A man is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images) (credit:Getty Images)
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Open Image ModalRunner John Ounao crying when he finds friends after several explosions rocked the finish of the Boston Marathon in Boston, Massachusetts, on April 15, 2013. At least two people were killed and 22 wounded when two explosions struck near the finish line of the Boston Marathon, sparking scenes of panic, police said. The streets were littered with debris and blood and paramedics raced off with stretchers as police locked down the area, witness said. TV footage showed an explosion sending up a white plume of smoke along the sidelines of the race. AFP PHOTO/John MOTTERN (Photo credit should read JOHN MOTTERN/AFP/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(14 of41)
Open Image ModalBOSTON, MA - APRIL 15: A man is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(15 of41)
Open Image ModalBOSTON, MA - APRIL 15: A man is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(16 of41)
Open Image ModalBOSTON, MA - APRIL 15: A runner reacts near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(17 of41)
Open Image ModalBOSTON, MA - APRIL 15: A member of the bomb squad investigates a suspicious item on the road near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(18 of41)
Open Image ModalBOSTON, MA - APRIL 15: Runners gather near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(19 of41)
Open Image ModalBOSTON, MA - APRIL 15: A police officer directs people around the finish line at the corner of Boylston Street and Massachusetts Avenue after two explosives detonated during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 28 injured after at least two explosions went off near the finish line to the marathon. (Photo by Darren McCollester/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(20 of41)
Open Image ModalBOSTON, MA - APRIL 15: Beacon Street near Kenmore Square remains empty for the use of emergency vehicles after two explosive devices detonated at the finish line of the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(21 of41)
Open Image ModalBOSTON, MA - APRIL 15: Police and runners stand near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 28 injured after at least two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(22 of41)
Open Image ModalBOSTON, MA - APRIL 15: A woman is helped from the scene near the finish line after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 28 injured after at least two explosions went off near the finish line to the marathon. (Photo by Darren McCollester/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(23 of41)
Open Image ModalBOSTON, MA - APRIL 15: Firefighters take postion on Boyltson Street near the finish line after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 28 injured after at least two explosions went off near the finish line to the marathon. (Photo by Darren McCollester/Getty Images) (credit:Getty Images)
Multiple People Injured After Explosions Near Finish Line at Boston Marathon(24 of41)
Open Image ModalBOSTON, MA - APRIL 15: A woman looks on as runners pass near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 28 injured after at least two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images) (credit:Getty Images)
Explosiones(25 of41)
Open Image ModalDos explosiones ocurrieron en la recta final del popular maratón de Boston, que se corre cada año en abril. (credit:AP)
Explosiones(26 of41)
Open Image ModalDos explosiones ocurrieron en la recta final del popular maratón de Boston, que se corre cada año en abril. (credit:AP)
Explosiones(27 of41)
Open Image ModalDos explosiones ocurrieron en la recta final del popular maratón de Boston, que se corre cada año en abril. (credit:AP)
Explosiones(28 of41)
Open Image ModalDos explosiones ocurrieron en la recta final del popular maratón de Boston, que se corre cada año en abril. (credit:AP)
Explosiones(29 of41)
Open Image ModalDos explosiones ocurrieron en la recta final del popular maratón de Boston, que se corre cada año en abril. (credit:AP)
Explosiones(30 of41)
Open Image ModalDos explosiones ocurrieron en la recta final del popular maratón de Boston, que se corre cada año en abril. (credit:Alamy)
Explosión(31 of41)
Open Image ModalEl momento de la explosión, imagen tomada de la estación local WBZ. (credit:AP)
Explosión(32 of41)
Open Image ModalPersonal de emergencia ayuda a los heridos. (credit:AP)
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Open Image ModalMedical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa) (credit:AP)
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Open Image ModalMedical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa) (credit:AP)
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Open Image ModalMedical workers aid an injured man at the finish line of the 2013 Boston Marathon following an explosion there Monday, April 15, 2013 in Boston. Two explosions shattered the euphoria at the finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa) (credit:AP)
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Open Image ModalMedical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa) (credit:AP)
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Open Image ModalMedical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa) (credit:AP)
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Open Image ModalPolice clear the area at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa) (credit:AP)
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Open Image ModalAn unidentified Boston Marathon runner is comforted as she cries in the aftermath of two blasts which exploded near the finish line of the Boston Marathon in Boston, Monday, April 15, 2013. (AP Photo/Elise Amendola) (credit:AP)
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Open Image ModalMedical personnel work outside the medical tent in the aftermath of two blasts which exploded near the finish line of the Boston Marathon in Boston, Monday, April 15, 2013. (AP Photo/Elise Amendola) (credit:AP)
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Open Image ModalMedical workers aid injured people at the finish line of the 2013 Boston Marathon following explosions in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa) (credit:AP)