The Boston Marathon bombing suspects had planned to blow up their remaining explosives in New York's Times Square, officials said Thursday.
New York City Police Commissioner Raymond Kelly said Dzhokhar Tsarnaev told interrogators from his hospital bed that he and his older brother had decided spontaneously Thursday night to drive to New York and launch an attack with their five pipe bombs and a pressure-cooker bomb like the ones that blew up at the marathon.
The plan fell apart after the Tsarnaev brothers were intercepted by police in a stolen car and got into a fierce gun battle that left Tamerlan Tsarnaev dead, Kelly said.
"We don't know if we would have been able to stop the terrorists had they arrived here from Boston," Mayor Michael Bloomberg said. "We're just thankful that we didn't have to find out that answer."
Dzhokhar, 19, is charged with carrying out the Boston Marathon bombing that killed three people and wounded more than 260, and he could get the death penalty.
He was interrogated in his hospital room over a period of 16 hours without being read his constitutional rights. He immediately stopped talking after a magistrate judge and a representative from the U.S. Attorney's office entered the room and gave him his Miranda warning, according to a U.S. law enforcement official and others briefed on the interrogation.
Tamerlan had come under scrutiny from the FBI, the CIA and Russian intelligence well before the Boston attack. The CIA had added Tamerlan's name to a terrorist database 18 months ago, after Russian intelligence flagged him as a possible Muslim radical, said officials close to the investigation who spoke on condition of anonymity because they were not authorized to discuss the case publicly.
That disclosure is certain to raise questions on Capitol Hill over the Obama administration missed an opportunity to thwart the Boston attack.
Kelly, citing interrogations carried out by the task force investigating the Boston Marathon attack, said that days after the bombing, the Tsarnaev brothers "planned to travel to Manhattan to detonate their remaining explosives in Times Square,"
"They discussed this while driving around in a Mercedes SUV that they hijacked after they shot and killed the officer at MIT," the police commissioner said. "That plan, however, fell apart when they realized that the vehicle they hijacked was low on gas and ordered the driver to stop at a nearby gas station."
The driver escaped and called police, Kelly said. That set off the gunbattle and manhunt that ended a day later with Dzhokhar captured and 26-year-old Tamerlan dead.
The suspects' father said Thursday that he is leaving Russia for the United States in the next day or two, but their mother said she was still thinking it over.
Anzor Tsarnaev has expressed a desire to go to the U.S. to find out what happened with his sons, defend his hospitalized son and, if possible, bring his older son's body back to Russia for burial.
Their mother, Zubeidat Tsarnaeva, who was charged with shoplifting in the U.S. last summer, said she has been assured by lawyers that she would not be arrested, but was still deciding whether to go.
This story has been updated.