WASHINGTON — The surviving Boston Marathon bombing suspect told FBI agents from his hospital bed that he and his brother were driven to the attack by jihadist radicalism sparked by the U.S. wars in Iraq and Afghanistan in which thousands of Muslims have died, a federal law-enforcement official familiar with the inquiry said Tuesday.
Dzhokhar Tsarnaev, 19, who lay in a Boston hospital with multiple gunshot wounds, also said he and his older brother, Tamerlan, learned how to make the pressure-cooker bombs used in the attack from an al-Qaida website, said the official, who spoke on condition of anonymity because details of the investigation are sensitive.
Tamerlan Tsarnaev, 26, died in a police shootout early Friday in which he hurled makeshift explosives at police before he was gunned down.
He is believed to have instigated the attack at the marathon that killed three people and injured more than 260 others after turning devoutly religious and possibly reading radical Islamic dogma on Internet sites or associating with radicals during visits to Russia, law-enforcement officials said.
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No evidence has surfaced so far that the two Chechen brothers were influenced by a foreign terrorist organization to carry out the worst terrorist attack on U.S. soil since Sept. 11, 2011.
But FBI agents have not foreclosed that possibility and will be conducting a worldwide investigation to examine the origins of their apparent radicalization, the law-enforcement official said.
The FBI expects to conduct a lengthy investigation to determine for certain whether they acted alone, were assisted by other conspirators or received any assistance along the way, the official said.
The investigation also will examine whether they were involved in an unsolved triple murder, apparently carried out on the 10th anniversary of the Sept. 11 attacks, in Waltham, Mass., the official said.
A friend of Tamerlan Tsarnaev, 25-year-old Brendan Mess, was among three young men whose throats were slit, apparently a day earlier than investigators originally thought, according to The Boston Globe, which first reported the possible linkage.
The Globe reported Tamerlan Tsarnaev had introduced Mess to the owner of a martial-arts center in the Allston neighborhood of Boston.
The FBI disclosed last week it had received a tip from Russia in 2011 that Tamerlan Tsarnaev had been radicalized, but that the bureau’s own three-month inquiry, which included an interview with him, found no evidence he was a terrorist threat.
His name was on a list circulated in the U.S. intelligence community, but his trip to Russia in January 2012 wasn’t noticed because his name was spelled wrong, the official said.
Republican leaders of the House Homeland Security Committee have demanded information from the FBI and intelligence agencies about what was known about Tamerlan Tsarnaev before the attack. But the law-enforcement official played down the significance of the inability to track his trip to Russia, saying he wasn’t considered a terrorism suspect, so his travel would not have set off any alarms.
Dzhokhar Tsarnaev, who sped his car through police officers during the shootout in suburban Watertown on Friday and escaped a manhunt for 19 hours, was captured that night after a resident found him in a boat resting in an area behind his house.
Badly wounded, he was questioned by FBI agents after regaining consciousness on Sunday.
On Monday, a federal magistrate and public defenders joined prosecutors in his heavily guarded room at Beth Israel Deaconess Hospital for a brief arraignment, in which he was formally charged with the capital crime of using a weapon of mass destruction, as well as malicious destruction of property resulting in death.