Set in motion just two months ago, the plan to explode a sport utility vehicle in Times Square was born of Faisal Shahzad's anger over U.S. treatment of Muslims, a law enforcement source told Newsday Wednesday.

In continuing interrogations of the accused car bomber Wednesday, investigators have learned much about Shahzad's plans and are establishing a firm timeline of

his movements between the United States and his native Pakistan, and between his home in Connecticut and his target in New York City.

"It appears from some of his other activities that March is when he decided to put this plan in motion," NYPD Commissioner Ray Kelly told the Senate Homeland Security and Governmental Affairs committee Wednesday. "He came back from Pakistan Feb. 3, 2010. It may well have been an indicator of putting something catastrophic in motion."

Shahzad has told investigators that he acted alone out of anger about U.S. treatment of Muslims after returning from a five-month trip to Pakistan with his family, but he has not been specific about the causes of his anger, a law enforcement official told Newsday.