If Tamerlan Tsarnaev was practicing a radical form of Islam, why didn't anyone recognize he was planning deadly violence against Americans?
His family says they began to notice a change in his behavior back in 2009, but what about the people he prayed with at his mosque in Cambridge?
Our David Mattingly is in Boston with that part of the story.
Authorities say the suspected Boston Marathon bombers wanted to attack New York City's Times Square. Their plans were hatched, according to investigators, after they allegedly shot and killed officer Sean Collier in Cambridge one week ago.
OutFront tonight: Democratic Congressman Dutch Ruppersberger. He's a ranking member of the House Select Committee on Intelligence.
Officials say the surviving bomb suspect and his brother planned an attack in Times Square.
"Last night we were informed by the FBI that the surviving attacker revealed that New York City was next on their list of targets, " New York City Mayor Michael Bloomberg said Thursday.
New York Police Commissioner Ray Kelly also said the suspects apparently came up with the plan spontaneously after the Boston bombings, as they talked in an SUV they hijacked.
Dzhokhar Tsarnaev initially told authorities that he and his brother, Tamerlan, had talked about going to New York City to "party." Further questioning by investigators revealed that they were planning to use their remaining explosives in Times Square.
Erin Burnett is live at 7pm ET on CNN from Times Square with the latest.