Last week, two ethnic Chechen brothers apparently went on a bombing and shooting rampage in Boston.
This week, security experts in Russia and the United States are debating why two years of warning signals apparently fell between the cracks.
"If we are talking about sharing sensitive information - Russia and America are not very good at it,” Andrei Soldatov said in Moscow, where he runs Agentura.ru
, a website that studies Russia’s security services.
In New York, Mark Galeotti is an expert on the Russian and American security services.
"You don't need to like another country to share intelligence with it," said Galeotti, who teaches global affairs at New York University.
This frank talk follows new evidence that there were clear warnings about the radical Islamist tendencies of Tamerlan Tsarnaev, the older brother of the pair.
In 2011, at the request of Russia, the American FBI questioned Tamerlan Tsarnaev, and reviewed his travel records and Internet usage.
The FBI said nothing substantive was discovered.
In January 2012, Tsarnaev, a Russian citizen, flew to Russia. He spent six months visiting friends and relatives in Dagestan and Chechnya, two Russian republics that have seen the greatest Islamist violence in recent years.
On his return to the United States last July, he was questioned at length by airport immigration officials at New York’s John F. Kennedy Airport.
Back in Boston, he created a publicly accessible YouTube site featuring videos, in English, Russian and Chechen, that advocated jihad, or Islamic holy war.
Some images bore symbols of the Caucasus Emirate, the main armed Islamist group in southern Russia.
In September, Tsarnaev applied for U.S. citizenship. The application was deferred after the Department of Homeland Security discovered he had been interviewed by the FBI.
A few weeks later, according to NBC News, Russian authorities asked the FBI again about Tsarnaev, saying that he had met with a known militant in Dagestan. The Russians said they never heard about a follow-up investigation.
“They had been warned by Russians that these guys might be tricky," said Vladimir Milov, a moderate Russian opposition politician. "I think it’s a terrible failure to be exact [that] they did not manage to find anything suspicious in the case, and this led to these tragic consequences.”
Last Friday, Russian President Vladimir Putin telephoned U.S. President Barack Obama. According to the Kremlin, both presidents agreed to improve information sharing.
But experts are skeptical.
"The problem is that a considerable level of suspicion has over the years set in on both sides," Galeotti said. "The American authorities do have the suspicion that the Russians will simply claim al-Qaida or similar tendencies about people they just don't like. And, likewise, the Russians very clearly feel that the Americans, like the other Western powers, sit on information that they [the Russians] really need in their own domestic struggles."
In addition, experts say, American and Russian security services may have fallen behind the times, searching for card carrying members of terrorist organizations.
On Sunday, the Caucasus Emirate denied any connections to the Boston violence, stressing that it has stopped attacking civilians and is at war with Russia, not the United States.
Some suggest the older Tsarnaev brother may fit the profile of a “lone wolf," a radical who learns his ideology and terror techniques in isolation, via the Internet.
Russian and American security services may still believe otherwise.
"Such people who might be involved in terrorism acts should be somehow tied with terrorist organizations and these terrorist organizations should provide them with financial support, logistical support, explosives, and training, etc., etc.,” said Soldatov, who also co-authored The New Nobility
, a book on Russia security services. “And when they fail to find such ties, such links, they just think it might not be very serious."
Galeotti agrees. "So these lone wolves are precisely people who are not ever recruited, they recruit themselves. And that is a challenge, because it is very, very difficult to identify them."
On the ground in Russia’s Northern Caucasus, insurgent networks may be more real. On Monday, Russian officials released the latest toll of violence by Islamist extremists.
During the first three months of this year, 47 shootings and bombings took 39 lives and left 105 wounded. In this low level, but steady insurgency, the victims were largely soldiers or policemen.