“Based on what I’ve seen so far, the FBI performed its duties,” Obama said. “Department of Homeland Security did what it was supposed to be doing. But this is hard stuff.”
Obama’s remarks came as the FBI expanded its investigation of the people who had contact with the two brothers suspected of carrying out the April 15 bombings. Tamerlan Tsarnaev, 26, was killed in a shootout with police four days after the bombings. His brother, Dzhokhar Tsarnaev, 19, was captured later the same day and faces federal charges that could lead to the death penalty.
Federal investigators are trying to trace the handgun, a 9mm Ruger, that the elder Tsarnaev used in the shootout. Two law enforcement officials said that an attempt was made to erase the serial number on the gun and that experts have been unable to restore all eight digits.
Law enforcement officials said several “persons of interest” in the United States and Russia are being investigated in connection with the brothers. One of the primary focuses is the seven months that Tamerlan Tsarnaev spent in Russia in 2012.
During that trip, Tsarnaev may have had contact with two suspected Russian militants in the country’s restive North Caucasus region, according to the law enforcement officials, who spoke on the condition of anonymity to discuss an ongoing investigation.
The FBI and other agencies began scrutinizing the elder Tsarnaev in 2011 after the Russian security service warned the bureau and the CIA of concerns that he was becoming increasingly radicalized and might travel to Russia to carry out an attack. He was questioned by FBI agents in Boston, but the inquiry concluded that he posed no threat. In January 2012, he traveled to parts of Russia where there are active Islamic insurgencies. He returned to the Boston area in July.
In the aftermath of the bombings, the FBI and Russian authorities are trying to reconstruct Tsarnaev’s activities in Russia. He spent most of his time with family members in Makhachkala, the capital of Dagestan, a Russian province where there is an active Islamist insurgency. Family members said he was not involved in any unusual activities.
But U.S. officials said the FBI is investigating information that Tsarnaev met with Mahmoud Mansour Nidal, who was suspected of recruiting for Islamist militants in Dagestan who are fighting the Russians. Nidal died in a gun battle with authorities last May in Makhachkala.
According to the officials, another line of inquiry is possible links between Tsarnaev and William Plotnikov, a Russian Canadian suspected of involvement with militants in the North Caucasus. Plotnikov was killed by Russian police in July and Tsarnaev returned to the United States a few days later, leaving behind a new Russian passport.