(CNN) -- Boston bombing suspect Dzhokhar Tsarnaev apparently was unarmed when he was wounded in a barrage of gunfire that ended with his capture after a tense standoff, sources told CNN Thursday.
No firearm was found in the boat where he was hiding, in the yard of a home in the Boston suburb of Watertown, Massachusetts, said several sources familiar with the investigation, from different agencies.
Earlier, Tsarnaev and his older brother, Tamerlan Tsarnaev, had allegedly shot and killed a Massachusetts Institute of Technology campus police officer sitting in a patrol car. Shortly afterward, the two engaged in a shootout with police. Tamerlan died after the shootout.
It's unclear why Dzhokhar may have hidden without any weapons.
Authorities have 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.
Dzhokhar Tsarnaev remains in fair condition at a Boston hospital, where he has communicated with authorities.
Authorities in the Russian region of Dagestan interviewed the suspects' parents in the search for clues and insight into what may have led the brothers to turn the Boston Marathon finish line into a gruesome scene of terror.
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Anzor Tsarnaev, the suspects' father, is expected to come to the United States to assist investigators. He told reporters he may leave as early as Thursday.
The suspects' mother, speaking to CNN's Nick Paton Walsh, didn't want to accept the reality of the bombing, saying it was fake.
"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," said Zubeidat Tsarnaev.
She has seen a video pushing the wild idea, she said, adding that there was no blood -- and that paint was used instead.
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. But she remained resolute that her sons, Dzhokhar, 19, and Tamerlan, 26 were not involved.
Dzhokhar faces terrorism and murder charges.
His mother is not coming to the United States.
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 semiautonomous region of Russia, officials said.
Tamerlan Tsarnaev's body remains unclaimed. Relatives in the United States have publicly said they are ashamed of the two young men. Several Boston-area imams have said they would feel uncomfortable presiding over Tamerlan's funeral.
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Detonated by remote
The brothers used a remote control device similar to those used to guide toy cars to detonate the two bombs in Boston, said Rep. Dutch Ruppersberger, a Maryland Democrat and member of the House Select Committee on Intelligence.
A law enforcement official told CNN Thursday that at least one of the two bombs -- the second to explode -- was detonated by remote control.
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.
Tsarnaev has indicated that his older brother planned the attack and described him and his brother as self-radicalized jihadists, according to a U.S. government source.
He has denied any direct influence from terror organizations such as al Qaeda.
The teenager cited the U.S. wars in Afghanistan and Iraq as motivating factors behind the attack, a U.S. government official said.
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He has been charged with using and conspiring to use a weapon of mass destruction resulting in death and one count of malicious destruction of property by means of an explosive device resulting in death.
Of the more than 260 people who were hurt in the marathon bombings, 33 were still hospitalized Wednesday night, according to a CNN tally. One person was in critical condition at Boston Medical Center.
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According to a source familiar with the investigation, authorities are looking into the possibility that Tamerlan Tsarnaev helped finance the bomb plot through drug sales.
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Putin: 'We were right'
Russian President Vladimir Putin on Thursday urged closer cooperation between other countries' security services after the Boston Marathon bombings.
"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 a victim of international terrorism itself. 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. They provided media support for them, financial support for them, political support -- sometimes directly, sometimes indirectly. But they always supported their actions in Russia.
"And we always told our partners, instead of general declarations you should have closer cooperation between our security services. And now these two criminals confirmed that we were right. "
He added, "Of course, we can speculate forever on the tragedy of the Chechen people when they were deported by the Stalin regime. But the Chechens were not the only victims."
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Dagestan has become a focus for investigators, especially given that Tamerlan Tsarnaev went there during a six-month trip to Russia last year.
Officials have been looking into what he may have done there. The young man is believed to have posted videos online tied to militant jihadists in the region.
On two occasions before that -- in March and late September 2011 -- Russian authorities asked U.S authorities to investigate Tamerlan Tsarnaev.
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."
Lawmakers are asking whether the FBI and CIA failed to share information.
Sources told CNN that Russia had separately asked the FBI and the CIA to look into Tsarnaev in 2011.
Sen. Lindsey Graham, a Republican who serves on several committees including Armed Services, 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.
"Some are racing to say that the FBI dropped the ball or the agencies weren't talking to each other, and that just doesn't seem to be the case," he added. Schiff is a ranking member of the Subcommittee on Technical and Tactical Intelligence.
The Tsarnaevs and Misha
A friend named Misha, whom Tamerlan met in the United States, steered the older brother toward a more devout view of Islam, Tamerlan's relatives have said.
His mother was impressed with the Armenian convert to Islam. He suggested that she cover her hair with a scarf, which she did.
"When Misha visited us ... he just opened our eyes, you know ... really wide about Islam. He was really, he's devoted and he's very good, very nice man," Zubeidat Tsarnaev said.
Tamerlan's uncle, Ruslan Tsarni, had a less favorable opinion.
"This person just took his brain," he said. "He just brainwashed him completely." Tamerlan, a former Golden Gloves boxer, left the ring and stopped listening to music under Misha's influence.
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NYC 'party' celebration
The brothers may have planned to celebrate the Boston Marathon bombings by driving to New York City to "party," according to Ray Kelly, the New York police commissioner.
Kelly said information collected from the surviving suspect included "something about a party or having a party."
"It may have been words to the effect of coming 'to party' in New York," Kelly said.
A man who was carjacked and held hostage -- allegedly by the two brothers -- just outside Boston last week said he thought he heard the two men say "Manhattan" in their conversation, which was in a language other than English, the commissioner said.
