Dzhokhar Tsarnaev, 19, told FBI interrogators in his Boston hospital room that he and his brother, Tamerlan, 26, in the aftermath of the bombings that killed three and wounded 260, intended to drive to New York City with their remaining five pipe bombs and one pressure cooker bomb, similar to the two set off during the marathon, said New York City Police Commissioner Ray Kelly.
In the aftermath of the marathon bombings, the brothers are suspected of killing a Massachusetts Institute of Technology police officer and hijacking a Mercedes-Benz SUV near Cambridge, Mass. After the car's driver escaped, Tamerlan Tsarnaev was killed in a firefight and a transit police officer was seriously wounded but survived.
With the driver's escape, the brothers' goal to drive to New York City "fell apart when they became low on gas, ordered the driver to stop at a gas station, and he fled and called police," Kelly said.
Dzhokhar Tsarnaev escaped after the shootout and was discovered Friday evening hiding in a boat in suburban Watertown, bleeding from multiple gunshot wounds. He has been in a hospital since then, and has spoken to FBI investigators from his bed.
"We don't know if we would have been able to stop the terrorists had they arrived here from Boston," said New York City Mayor Michael Bloomberg. "We're just thankful that we didn't have to find out that answer."
A 'spontaneous' plan
Kelly said the city learned of the brothers' plans through the FBI's Joint Terrorism Task Force, which includes New York City Police Department officials. He said the brothers had "spontaneously" decided on Times Square as a target and discussed heading there as they drove around in the stolen SUV.
Tsarnaev initially told interrogators that he and his brother planned to "party" in New York before admitting to the Times Square plan in a later interview.
"He was a lot more lucid and gave much more detail in the second interrogation," Kelly said.
The revelation of the brothers' desire to continue their bombings and to strike New York City is perhaps the most disturbing to emerge since the April 15 marathon bombings, in which a pair of shrapnel-packed pressure cooker bombs exploded near the race finish line.
A federal law enforcement source characterized the Times Square plan as "aspirational rather than operational." Still, the statements Tsarnaev made about the plot contributed to the FBI's spreading out to various locations in the New York metropolitan area to follow leads, he said.
Bloomberg said the surviving Tsarnaev brother told the FBI the pair "had built those additional explosives, and we know they had the capacity to carry out the attacks. If, God forbid, they had arrived in New York City and gone to Times Square, one thing's for sure, they would have seen an enormous police presence."
Times Square was the target of terrorism in May 2010 when Pakistani immigrant Faisal Shahzad planted a bomb similar to the ones used at the marathon in an SUV. Street vendors noticed smoke coming from the vehicle and alerted authorities, who disabled the bomb. Shahzad is serving life in prison.
"The fact is, New York City remains a prime target for those who hate America and want to kill Americans," Bloomberg said.
Kelly said Dzhokhar Tsarnaev was photographed in Times Square with friends on or before April 18 last year and that he was in the city again in November.
"We don't know if those visits were related in any way to what he described as the brothers' spontaneous decision to target Times Square," Kelly said. "The NYPD Intelligence Division is actively investigating to determine Dzhokhar's movements in New York City, as well as who he might have been with here."
Britney Smith, a friend of Dzhokhar Tsarnaev's whom FBI agents interviewed at her mother's Ridge home April 19, said he had spoken with her during a trip to Manhattan last year.
"He told me Times Square was his favorite spot," said Smith, 23. "He said he loved New York."
Meanwhile, FBI agents investigating the Boston bombings are scouring for clues in both the United States and abroad. Early Thursday morning, authorities found numerous fireworks shells dumped in a used clothing donation bin at a Watertown parking lot, the source said.
They believe explosive powder emptied from those fireworks may have been used to help construct the marathon bombs, the source said.
In the Russian republic of Dagestan, FBI agents completed a round of interviews with Zubeidat Tsarnaeva and Anzor Tsarnaev, the parents of the suspected bombers, the source said. The father has said he plans to travel to the United States in the coming days. Both parents have insisted their sons are innocent. The source said that Tamerlan Tsarnaev exchanged text messages with his mother, saying that he was ready to die for Islam.
"There's a text involving the mother where they talk about the son being ready to die," the source said.
Investigators are examining whether radical Islamist groups in the republics of Dagestan and Chechnya -- where the brothers have roots -- influenced Tamerlan Tsarnaev's shift toward radical Islam. He spent six months in the region in the past year and was listed on terrorism watch lists compiled by the U.S. government, the source said.
The FBI has found jihadist videos on Tamerlan Tsarnaev's YouTube channel and believe the brothers learned to make pressure-cooker bombs from instructions in an al-Qaida online magazine, the source said. Investigators believe the brothers were motivated by perceived American slights against Islam and the wars in Iraq and Afghanistan, the source said.
Dzhokhar Tsarnaev remains in fair condition at Beth Deaconess Medical Center. The surviving brother had been providing "valuable" information to interrogators -- including about the planned trip to New York -- when a federal magistrate judge came to the hospital and read him his Miranda rights 16 hours into a round of interviews, the source said.
The source said the FBI believed it should have had 36 to 48 hours to question Tsarnaev under the pre-Miranda public safety exemption. Tsarnaev stopped answering questions after being read his rights, the source said.
"We don't know what more he would have said," the source said. With Matthew Chayes