Story highlights A congressman says suspects "likely" planned Boston attacks, then changed plans

Russia voiced concerns to the U.S. about one suspect, his mother, sources say

Police: Suspect told investigators he and his brother decided "spontaneously" to bomb NYC

Dzhokhar Tsarnaev, 19, was "more lucid" the second time he was interviewed, police say

Days after allegedly causing death and devastation at the finish line of the Boston Marathon, two brothers "spontaneously" decided to head to a new place to unleash terror -- New York City -- that city's mayor said.

Dzhokhar Tsarnaev, the surviving suspect in the Boston bombings, told investigators that he and his brother decided to bomb Times Square as they talked the night of April 18 in a Mercedes SUV they'd just carjacked, New York City Police Commissioner Ray Kelly said.

The 19-year-old initially told investigators from a Boston hospital bed that he and his brother, Tamerlan Tsarnaev, had talked about going to New York to "party." Then he offered a new account during a second round of questioning Sunday evening into Monday, during which Kelly said Dzhokhar was "a lot more lucid" than the first time he was interviewed.

The brothers had five pipe bombs and a "pressure-cooker bomb" -- the latter similar to the bombs used in the Boston blasts -- with them in the SUV that they could have used in New York, Kelly said.

Instead, their plan "fell apart" when the SUV ran low on fuel in the Boston area and the Tsarnaevs ordered the driver to pull into a gas station, Kelly said. The driver escaped during the refueling, he said, and police subsequently caught up with the Tsarnaevs -- first in a shootout after which 26-year-old Tamerlan died, then by capturing Dzhokhar on Friday.

"We don't know that 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."

Rep. Mike Rogers, chairman of the House Intelligence Committee, said investigators believe the Boston bombing suspects were planning another attack "likely in the Boston area."

This image from VK.com shows Dzhokhar Tsarnaev in New York's Times Square.

"The notion they decided to go to New York was a rushed event after this thing unraveled on them," the Michigan Republican said.

Photos: Boston bombings suspect: Tamerlan Tsarnaev Photos: Boston bombings suspect: Tamerlan Tsarnaev Tamerlan Tsarnaev, one of the Boston Marathon bombing suspects, was the subject of an April 2009 photo essay that appeared in a graduate school magazine at Boston University. According to the article, he had hoped to become a naturalized American and make the U.S. Olympic boxing team. Authorities say an overnight shootout with police left him dead on April 19, 2013. Hide Caption 1 of 8 Photos: Boston bombings suspect: Tamerlan Tsarnaev Tsarnaev answers a call while walking to boxing practice at the Wai Kru Mixed Martial Arts center in Boston. Hide Caption 2 of 8 Photos: Boston bombings suspect: Tamerlan Tsarnaev Tsarnaev practices boxing at the Wai Kru Mixed Martial Arts center. Hide Caption 3 of 8 Photos: Boston bombings suspect: Tamerlan Tsarnaev Tsarnaev shows how he strengthens his ankles, according to the photo essay. The photographer did not want to be named for this story. Hide Caption 4 of 8 Photos: Boston bombings suspect: Tamerlan Tsarnaev Though he had lived in the United States for five years, Tsarnaev said in the essay: "I don't have a single American friend. I don't understand them." Hide Caption 5 of 8 Photos: Boston bombings suspect: Tamerlan Tsarnaev Tsarnaev works out. Hide Caption 6 of 8 Photos: Boston bombings suspect: Tamerlan Tsarnaev Tsarnaev stretches during boxing practice. Hide Caption 7 of 8 Photos: Boston bombings suspect: Tamerlan Tsarnaev Tsarnaev tapes up his hand. Hide Caption 8 of 8

Photos: Photos: Suspects tied to Boston bombings Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Dias Kadyrbayev, left, with Boston Marathon bombing suspect Dzhokhar Tsamaev in a picture taken from the social media site VK.com. Kadyrbayev is expected to plead guilty August 21 to charges in connection with removing a backpack and computer from Tsamaev's dorm room after the April 2013 bombing, according to a defense lawyer. Hide Caption 1 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Bombing suspect Tamerlan Tsarnaev was killed during the shootout with police in Watertown, Massachusetts, on April 19, 2013. He is pictured here at the 2010 New England Golden Gloves. Hide Caption 2 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Dzhokhar Tsarnaev was captured in a Boston suburb on April 19, 2013, after a manhunt that shut down the city. In July, he pleaded not guilty to killing four people and wounding more than 200. Hide Caption 3 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – From left, Azamat Tazhayakov and Dias Kadyrbayev went with Boston bombing suspect Dzhokhar Tsarnaev to Times Square in this photo taken from the social media site VK.com. A federal grand jury charged Tazhayakov and Kadyrbayev with obstructing justice and conspiracy to obstruct justice relating to the removal of a backpack from Tsarnaev's dorm room after the bombings. Tazhayakov was convicted of conspiracy and obstruction charges in July 2014. He faces up to 25 years in prison at his sentencing in October. He has filed an appeal. Hide Caption 4 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Robel Phillipos, a U.S. citizen, was also arrested on May 1, 2013 . He was charged with lying to federal agents about the bombing, according to court papers. Hide Caption 5 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Phillipos, Tazhayakov and Kadyrbayev are accused of removing items from Tsarnaev's dorm room after the bombings on April 15, 2013. The items they took included a backpack containing fireworks that had been "opened and emptied of powder," according to the affidavit. Hide Caption 6 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – The FBI released photos and video on April 18, 2013, of two men identified as Suspect 1 and Suspect 2 in the deadly bombings at the Boston Marathon. They were later identified as Dzhokhar Tsarnaev, 19, and his brother Tamerlan Tsarnaev, 26. Hide Caption 7 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Boston Police released surveillance images of Dzhokhar Tsarnaev at a convenience store on April 19, 2013. Hide Caption 8 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – The FBI tweeted this photo on April 19, 2013, and urged Watertown residents to stay indoors as they searched for the second suspect. Hide Caption 9 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – The FBI released photos and video on April 18, 2013, of two men it called suspects in the deadly bombings and pleaded for public help in identifying them. The men were photographed walking together near the finish line. Hide Caption 10 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – A man identified as Suspect 2 appeared in this photograph by bystander David Green, who took the photo after completing the Boston Marathon. Green submitted the photo to the FBI, he told Piers Morgan in an interview. Hide Caption 11 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – The man identified as Suspect 2 appears in a tighter crop of David Green's photo. Hide Caption 12 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Authorities later identified Suspect 1 as Tamerlan Tsarnaev. Hide Caption 13 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Suspect 2 was identified as Dzhokhar Tsarnaev. Hide Caption 14 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Suspect 1 walks through the crowd. Hide Caption 15 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Suspect 1 walks through the crowd. Hide Caption 16 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Suspect 1 walks through the crowd. Hide Caption 17 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Both suspects are seen walking through the crowd. Hide Caption 18 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Suspect 2 walks through the crowd. Hide Caption 19 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Suspect 2 walks through the crowd. Hide Caption 20 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – A photo released by the FBI highlights Suspect 2. Hide Caption 21 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – A photo released by the FBI highlights Suspect 2. Hide Caption 22 of 23 Photos: Photos: Suspects tied to Boston bombings Suspects tied to Boston bombings – Suspect 2 walks through the crowd. See all photography related to the Boston bombings. Hide Caption 23 of 23

There is no evidence that New York City is currently a target of a terror attack stemming from the Boston bombings, Kelly added. Still, he said authorities are investigating two visits that the surviving suspect made to New York City last year.

In one of those trips, in April 2012, Dzhokhar Tsarnaev is photographed in Times Square.

One person pictured in that picture was in federal custody Thursday, as he's been for the last six days, on alleged visa violations. This man, whom a federal law enforcement source said Dzhokhar shared a cell phone with, was originally detained last Friday with another person when federal agents swarmed a residence thinking Dzhokhar might be inside, a federal law enforcement source said.

Neither of these two detained men -- both foreign exchange students from Kazakhstan at the University of Massachusetts-Dartmouth, where Dzhokhar also was enrolled -- has been linked to the Boston Marathon attack. Yet investigators hope they can better piece together the suspected bombers' movements before and after the marathon.

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"These guys are not being cut loose immediately, and there's a reason why," the federal law enforcement source said.

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Sources: Russia raised concerns about mother, son

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While investigators continue to look into the Boston bombings, the killing of a Massachusetts Institute of Technology campus police officer and a violent chase and shootout in Watertown, Massachusetts -- all of which authorities have blamed on the Tsarnaev brothers -- the probe has also been focused some 5,500 miles away in the semi-autonomous Russian republic of Dagestan.

That's where the suspects' parents live and spoke to reporters Thursday.

Their mother, Zubeidat Tsarnaev, told CNN's Nick Paton Walsh that she didn't want to accept the reality of the bombing, saying it was fake. She has seen a video pushing the wild idea, she said, adding that there was no blood -- and that paint was used instead.

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"That's what I want to know, because everybody's talking about it -- that this is a show, that's what I want to know. That's what I want to understand," she said.

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But her disbelief broke down when she spoke of the victims.

"I really feel sorry for all of them. Really feel sorry for all of them," she said, her voice cracking even as she remained resolute that her sons were not involved.

While her husband Anzor Tsarnaev has said he plans to fly to the United States -- though those plans may be in limbo after Zubeidat said she called for an ambulance for him on Thursday in Makhachkala -- his wife isn't planning to join him.

She's wanted on 2012 felony charges of shoplifting and property damage in Massachusetts, according to court officials.

The family lived there before she jumped bail; the parents moved the same year to Dagestan.

A year before, Zubeidat and her son Tamerlan were both added by U.S. authorities to the Terrorist Identities Datamart Environment, or TIDE, database -- a collection of more than a half million names maintained by the National Counterterrorism Center, an intelligence official said.

That came as Russia raised concerns to U.S. authorities about her and her son, sources told CNN.

Zubeidat Tsarnaev said the FBI had visited her family "several times" in 2011 with questions about Tamerlan's "Islamic interests."

A senior U.S. official with direct knowledge of information from the Russians said that the case then "was extremely thin," adding that Russia wanted Tamerlan Tsarnaev questioned to see if he and others had become "radicalized." U.S. authorities closed the case a few months after opening it.

Putin: 'We were right'

Russian President Vladimir Putin on Thursday urged closer cooperation between other countries' security services in the wake of the Boston attack

"If we combine our efforts, we will not suffer blows like that," he said during a live televised call-in session in Moscow on Thursday.

The Tsarnaevs are originally from the embattled Russian republic of Chechnya but fled from the brutal wars there in the 1990s. The two brothers were born in Kyrgyzstan and moved at different times to the United States.

In his first on-camera comments since the bombing, Putin also lashed out against those in the West who have slammed Russia for human rights abuses in its actions toward Chechnya.

"Russia is among the first victims, and I hate it when our Western partners call our terrorists -- who committed some heinous crimes in Russia -- when they call them freedom fighters and never call them terrorists. They supported them," said Putin, accusing unnamed people or groups of providing Russia's foes with political, financial and "media" support.

And U.S. authorities have come under fire at home, with lawmakers asking if the FBI and CIA failed to share information. Sources told CNN that Russia had separately asked the FBI and the CIA to look into Tamerlan Tsarnaev in 2011.

Sen. Lindsey Graham, a South Carolina Republican, said Thursday he believes "ultimate blame" for the attacks goes to the Obama administration.

"The FBI and the CIA are, they have great people but, you know, we're going backwards in national security. Benghazi and Boston to me are examples of us going backward," he said

But a ranking Democrat on a House intelligence subcommittee said Thursday he does not see an intelligence-sharing failure.

"This information was put in a database, it was shared among different agencies, it was shared with a joint terrorism task force, and that's exactly what should happen," U.S. Rep. Adam Schiff, D-California, told CNN, referring to the TIDE database.

Sources: Suspect was unarmed in boat

More details, meanwhile, continue to emerge about the April 15 bombings as well as authorities' engagement days later with the two suspects.

A law enforcement official told CNN Thursday that at least one of the two bombs -- the second to explode -- was detonated by remote control. Rep. Dutch Ruppersberger, a Maryland Democrat and member of the House Select Committee on Intelligence, said that the brothers used a remote control device similar to those used to guide toy cars.

While video taken near the scene of the explosions shows Dzhokhar Tsarnaev talking on a cell phone, it is not known whether he used it to trigger a device, a law enforcement official said.

Those twin blasts killed three people and injured more than 260 others, 14 of whom had limbs amputated. As of Thursday evening, 34 of those wounded were still being treated at Boston hospitals, including one patient in critical condition.

The manhunt for those responsible ended last Friday, when Dzhokhar Tsarnaev was captured after a tense standoff after he'd hidden in a boat in the yard of a home in the Boston suburb of Watertown, Massachusetts.

The teenager was unarmed when he was wounded in a barrage of gunfire, and there was no firearm found in the boat, said several sources from difference agencies familiar with the investigation.

Authorities previously said in a criminal complaint that there was a standoff involving gunfire before Dzhokhar's capture. Watertown Police Chief Edward Deveau told CNN's Wolf Blitzer on Saturday that it was his understanding that the suspect fired from the boat.

This came after Tsarnaev and his older brother allegedly shot and killed Massachusetts Institute of Technology campus police officer Sean Collier in Cambridge.

The Middlesex County District Attorney's Office hopes to bring charges against Dzhokhar Tsarnaev for his alleged role in incidents last week in Cambridge and Watertown, spokeswoman Stephanie Guyotte said Thursday.