La tragedia que enluta a Boston

Runner 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

BOSTON, 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. Jim Rogash/Getty Images/AFP== FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==

BOSTON, 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. Alex Trautwig/Getty Images/AFP== FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==

CJX30. BOSTON (MA, EE.UU.), 15/04/2013.- Una mujer abraza a su padre después de que se registraran dos explosiones cerca a la línea de meta de la 117 Maratón de Boston, Massachusetts (EE.UU.) hoy, lunes 15 de abril de 2013. Al menos dos personas murieron y otras 23 resultaron heridas en el hecho, según la Policía, que confirmó el hallazgo de al menos un artefacto de fabricación casera en la zona. EFE/CJ GUNTHER

BOSTON, 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. Darren McCollester/Getty Images/AFP== FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==

US President Barack Obama pauses as he speaks on the Boston marathon explosions on April 15, 2013 in the Brady Briefing Room of the White House in Washington, DC. 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. AFP PHOTO / Mandel NGAN

KOCH04 MOSCÚ (RUSIA) 16/04/2013.- Una mujer coloca unas flores ante la embajada estadounidense en Moscú (Rusia) hoy, martes 16 de abril de 2013. Los principales líderes mundiales mostraron hoy su conmoción y solidaridad con el pueblo y las autoridades estadounidenses tras los atentados registrados en el maratón de Boston (EE.UU.), que causaron este lunes tres muertos y más de 140 heridos. EFE/ Yuri Kochetkov

BOSTON, MA - APRIL 15: A runner sits 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. Alex Trautwig/Getty Images/AFP== FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==

JLX38 BOSTON (ESTADOS UNIDOS) 16/04/2013.- Un hombre observa las bolsas con los objetos personales de los corredores reunidas junto a la meta de la maratón de Boston, mientras continúan las investigaciones en el escenario de las dos explosiones que causaron ayer la muerte a tres personas y heridas a más de un centenar, en Boston, Massachusetts, Estados Unidos, hoy martes 16 de abril de 2013. EFE/MATT CAMPBELL

BOSTON, MA - APRIL 15: Boston Police guard an area at the one mile checkpoint 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. Alex Trautwig/Getty Images/AFP== FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==