Boston University holds memorial service for bombing victim Lu Lingzi
London Marathon runners silence for Boston bomb victims
Obama in Boston to mourn bombing victims
FBI releases photos of bombings suspects
Suspicious envelope found in US Senate office building
Boston mourns bombing victims
Security beefed up worldwide after Boston blasts
Obama delivers statement on Boston Marathon explosions
FBI releases Boston Marathon bomb details
File photos: horrible scenes in 9/11 terrorist attacks
Explosions at Boston Marathon kill 3
