You don't even have to go to conspiracy theories. The dead Boston Marathon bombing suspect was already an FBI case, on advice from Moscow.
Look, you can't prevent everything, but thousands of foreign civilians and American military dead and injured in foreign wars, a concentration camp in Guantanamo, the loss of habeas corpus and Miranda Rights, black-ops around the world and the blowback they bring, and you can't stop a couple of angry young men you already know about? Weren't we told all of these abominations were necessary for 'security' (whose?)?
America, you're doing it fucking wrong.
Just had a thought... Did the FBI think they'd turned this guy? They'd interviewed him, but not jailed him. Something tells me they'd try to bury that story if they thought they'd been running him. So much of this account screams: 'BULLSHIT!' Wonder who shot up the boat... Someone's head's gonna roll, but probably not the right one, as usual.